The following instructions and procedures are meant to be used as a general guide in creating Four Color Process separations
to be used for screen-printing on textiles. The parameters are
generalized and each artist would use their own judgment to determine
the outcome of the finished piece. Make sure you document all
adjustments so if you end up with pleasing results, you know to make
similar adjustment the next time. Expect to rework any set of
separations at least once and probably more than that when first
starting out. The documentation will help when deciding what
adjustments are necessary on the rework. The adjustments made for this
article are done in Photoshop 6.0. If you are using a different
version, the information will be the same, but the settings may not be
located the same places.
Make a duplicate of the original so we can check against it as we go
through the separation procedure. Our goal is to end up with a set of
separations that look like a weak or washed out version of our
original. We want this because of the dot gain we will experience when
we print. If out finished separations look great on the monitor, then
our print will probably look muddy.
Image
Duplicate…
Next we need to address is the resolution. We would want to work
with a resolution that is approximately 2-2 ½ times the LPI or halftone
size (number of dots per linear inch) we will use in our output of the
separations. Since most shops work with a45-65 LPI, our resolution
should be between 100 and 150. If the resolution is too high, some of
the information might be too fine to hold when we output the information
and will be discarded by the program.
Image
Image Size…
Resolution
We need to make sure we are in CMYK. If not, go to
Image
Mode
CMYK Color
Although our artwork is now separated, it is separated for the offset
process, since Photoshop was written for the offset trade. If we use
the separations the way they are, we will probably get a muddy print.
Because of this, we have to modify many of the parameters.
Making adjustments so the image will have a little more life is done as follows:
Image
Adjust
Brightness/Contrast…
I like to brighten my image a little and then increase the contrast
so my light areas jump forward and my shadow areas drop back, but I
don’t loose detail. Often, my colors become more intense and make the
image more appealing for a t-shirt. Once satisfied with the results,
hit OK.
We are now ready to adjust each of the colors and
compress the dot range so it is suitable for screen-printing. It will
be necessary to take the information that is less than 15% and more than
80% and compress them towards the center to our usable range. We will
still have information that is less than 15% and more than 80%, but the
bulk of that information will sit where we can use it. The reason we do
this is because holding dots that are less than 15% for most printers
is difficult. Dots of over 80% will probably print as a solid area due
to dot gain or dot spread. By compressing the range, we will have a
very usable set of separations.
Image
Adjust
Curves…
Do not make adjustments with the CMYK showing. Go to the arrow at
the right and choose the Yellow. Take the bottom of the diagonal line
and move it to the right until you see 15%. Now take the top of the
diagonal and pull it down until it reads 85%. Do the same to the
Magenta and Cyan. There are times when less of an adjustment will be
needed and it will be up to each artist to make that decision.
Next, we have to make adjustments on the black, which is
the K. Because the black is very strong, it wills over power the other
colors unless we make a more dramatic adjustment. We also only want
black in the darkest shadow areas so choose the Black and slide the
bottom of the diagonal up to 30% and pull the top of the diagonal up to
70%. If you feel you have lost too much information, back off the
amount of compression.
When the Preview button is hit, you will be able to see how much of
an adjustment was made. If you are unhappy with the results, go into
the history and delete that which you are unhappy with and make new
adjustments.
Now we have to add some information and make several additional adjustments.
File
Page Setup…
Screens…
Remove the check mark next to “Use Printer’s Default Screens” so you
can choose your own Frequency (LPI/Half-tone) and insert that
frequency. For manual printers, I would recommend 45 and for automatics
55.
Next, change the Shape to Ellipse. An ellipse have a
little less dot gain and more surface so it will be a little easier to
hold on a screen.
We are now ready to address the Angle. Working with the
given angles will be difficult since the Black is at 45 degrees and the
dots will sit on the horizontal strands of mesh and could easily create a
moiré or saw tooth. The Yellow is 90 degrees and would sit on the
vertical strands and could also create a moiré or sawtooth. By changing
the angles 2-4 degrees, we may avoid these problems.
Color Offset Angles Screen-print Angles
Yellow 90 degrees 86-88 degrees
Magenta 75 degrees 71-73 degrees
Cyan 60 degrees 56-58 degrees
Black 30 degrees 26-28 degrees
Most screen-printers will have three colors that print well and one
that always seems to moiré. Since we are not interested in creating a
rosette pattern as offset printers are, we are not forced to use all
different angles. For example, if the Magenta seems to be the color
that usually has a moiré problem, we can eliminate that angle (71-73
degrees) put the Magenta to the 86-88 degree angle, move the Yellow to
the same angle as the Black (26-28 degrees) and not have a moiré
problem.
Another possible solution to the moiré problem is using
only one angle for all colors. I like to work with a 50 LPI with a 61
degree angle for all colors. Test a variety of angles on various mesh
sizes with the LPI you will be using and select the angle the seems to
have the least probability of moiré. Since the rosette pattern is not
important to us, this will also work.
Once the Frequency, Angles and Shape have been selected
and OK has been hit, we need to select a few more items in Page Setup.
Check the Calibration Bars, Registration Marks, Center Crop Marks and
Labels, then hit OK.
We will need to make further adjustment to our image before we can print the separations. Go to
Edit
Color Settings…
Settings:
Custom
Working Spaces
CMYK:
Hit the arrow and go to
Custom CMYK
Once in that screen, go to
Name:
Change to Screen-print, then go to
Ink Options
Dot Gain:
36%
Some printers can use a little less dot gain and others more. This
is only a starting point. If you print with a lot of pressure, increase
the dot gain and if you use a minimal amount of pressure, decrease the
dot gain. Printers will not use less than 25% dot gain due to the
nature of the inks we use and the process itself.
In the same screen, go to
Separation Options
Separation Type:
UCR
Under Color Removal is the taking away of color from where the black
will print so there will be room for the black. Without UCR, the black
areas could turn brown.
Still in Separation Options, go to
Total Ink Limit
250%
Enter OK until you are out of all screens.
You are now ready to output film, print a sample and see what adjustments are ne
Tuesday, October 2, 2012
Controlling Color Throughout the Screen Printing Process
0 komentar Diposkan oleh Unknown di 10/02/2012 08:56:00 PM
By Ray Bohnen
All "output for hire" industries have their fair share of idiosyncrasies, and screen printing is no exception. But one lesson that applies to all of them is this: Those who pay attention to the details of process and quality control typically get to go home at the end of the day rather than stay and rework digital artwork or reprint jobs. The strict habits and practices developed when implementing process and quality control create a solid foundation for the introduction of other technologies, among them the tools and techniques for color management.
When I talk about color management, I am referring to the process in which ICC-compliant software is used to help predict and quantify the digital color content in a printing environment of any kind. The tool used to describe this content is called an ICC profile. Ultimately, the data describing the "color space" of the printing device (and all its settings) can be used to make sure imaging files are prepared correctly well before they arrive at the press. This makes the entire workflow more efficient and color more accurate. Use of ICC profiles is not an emerging technology, nor something to watch for in the future. It is a concept that is here now and being used in print shops of all descriptions around the globe. Applied to any flatbed, roll-fed, digital, or screen-printing process, color management can save time and money while enhancing the color-imaging workflow.
Simply put, if you can establish and communicate a description of your final color-output scenario, you provide everyone in the workflow with a target to aim for and a benchmark against which they can assess the results. This works just as well for screen printing as it does for any other printing process.
With this in mind, I propose to discuss how ICC-compliant software can be used to help predict and quantify the digital content in a screen-printing workflow. I will talk about each stage, including content creation, prepress, screenmaking, and printing on press. I also will review the issues that affect color management and compare traditional solutions to ICC-compliant strategies. My objective is to show you that implementing color management at the front end of the workflow will minimize the need to correct color on press.
Content creation
Content creation is an interesting aspect of any output-for-hire workflow, if only because we rarely have any control over it. Nevertheless, we are expected to understand the content creator´s expectations. Oh, and by the way, the language spoken by content creators is not always understood by the industries that will be outputting their creations. However, the designers and content creators leave bread crumbs and other tell-tale signs along the path. If we are to implement an ICC workflow, we need to identify them and incorporate them into our workflow so that we can control and streamline the process.
Most digital files are created outside of the screen shop by designers or creative agencies using industry standard applications, such as Photoshop, Illustrator, QuarkXPress or InDesign. These files are supplied in their native formats, or possibly as Portable Document Format (PDF) files. In most cases, whether the creator of the artwork knows it or not, the digital content color settings of the file have already been optimized for some type of commercial printing situation. However, unless the content creator has an understanding of the color-management tools in their applications, we may be left to guess what they are passing along to us.
The issues These digital files are usually created using color configurations, color settings, preferences and color libraries that are configured to default settings for offset printing. This means that what the content creator saw on his or her screen is not what we will print. Furthermore, when we view the digital files in our shop, what we see will not be what we print.
If PDF files are supplied, we are certain to get a mix of both properly and improperly created files. Ideally, the PDF files are created to conform to a specification such as PDFX-1a. PDFX-1a requires that all elements within the layout be in the CMYK color space, that all fonts are included, and that profiles describing the source and destination color spaces are included. Unfortunately, in many cases we do not receive PDFX-compliant files.
The traditional approach In a traditional scenario, we would send the supplied file onto screenmaking without determining the color settings it contains. This makes the results we can deliver on press unpredictable and inevitably leads to trouble.
The ICC approach More and more screen printers who have implemented color-management systems also have developed communication methods to help educate content creators about proper file preparation. This approach is consistent with the color-management principle of anticipating challenges as early in the workflow as possible. Remember that while content creators aren´t inherently enamored with color-management technology, more and more of them are aware of how ICC profiles are created and used. Reaching out to content creators, especially those at large clients, could be regarded as the first step in the color-management process.
Some screen printers are using an even more aggressive strategy that involves beefing up their creative departments as a way of pre-empting problems involved with incoming files. For some, creating content in house for clients has evolved into a significant source of additional revenue.
In any case, there is some point in the workflow in which the image file will have to be either created or modified to deliver the benefits of an ICC workflow in your shop. If the content creator doesn´t do it, your staff will have to.
Order entry and prepress
In many ICC workflows, the order-entry stage is more than the recording of customer information, job parameters, and scheduling. It also is an opportunity to anticipate and correct problems that may appear later in the workflow. For shops implementing ICC color management, order entry can function as a staging area in which some of the preflighting processes discussed in this article take place. Color-separation films produced by outside sources also may be checked at this stage. It all depends on how you set up your workflow. But whether filmmaking is outsourced or performed in house, incoming files need to be checked or preflighted before they are used to produce positives.
The issues Opening and checking the digital files takes time and requires a high level of application experience in order to define potential problems or catch inconsistencies and errors. If a problem is not caught, it will mean wasted time and material, both of which lead to increased costs.
The traditional approach Typically all supplied digital content is opened and checked for missing fonts and placed, linked, or missing graphics. We also determine if the resolution is sufficient and examine file size, orientation, and other basic parameters. But this doesn´t help us with color accuracy.
The ICC approach Preflighting is a term that comes from the preflight check that pilots perform on aircraft prior to taking off. In graphics reproduction, instead of opening each file to ensure that all the required parameters are in place, we can use an automated preflighting software package to do this for us. This software issues a report that tells us whether we have a pass or fail situation. It is useful for checking all non-color problems, but the software really comes into its own when it comes to inspecting the color settings. Examples of preflighting software are FlightCheck from Markzware (www.markzware.com) and PreFlightPro from Extensis (www.extensis.com). These applications allow the user to apply prede-fined settings, or create settings that apply to the expectations of their workflow.
In addition to file resolution, file size, and image orientation, this workflow-automation tool has the capability to define the color spaces (RGB, CMYK, or other) and determine whether supplied graphics have an embedded ICC profile, as shown in Figure 1. This is the heart of an ICC workflow. This embedded file serves as a digital road map that tells us where the file is coming from. It becomes important in prepress, where it allows us to effectively preview the file the way the content creator envisioned it.
Preflighting software verifies that all design components are intact and properly assembled and identifies any embedded ICC profiles.
A drop folder, or hot folder, is a typical preflighting tool. The digital content is dropped into the folder, where the software quickly and efficiently checks the parameters that we have defined, then creates a text report. Upon reviewing the text report, our operators can either pass the digital content to the next stage in the preparation for printing, or open the offending graphic(s) and make necessary changes.
More issues Now we can consider the color settings the content creator used when assembling or creating the content. This process will tell us whether the colors we are seeing on our monitors are what the content creator was seeing and what the content creator wanted to print.
The traditional approach We use the same graphics applications that the content creators use. We also may use the same default color settings, or preferences, within these applications. Visits to customer sites, as well as communication with end users, have convinced me that default color settings are used more than 85% of the time. These default settings are created within applications such as Adobe Photoshop, Adobe Illustrator, Adobe PageMaker, Adobe InDesign, Quark XPress, and the like. All of the Adobe applications use a subset of the color settings used for Photoshop, which at least creates consistency within the Adobe program suite.
The most important thing to be aware of at this stage is that the default color settings create an onscreen preview with a specific appearance for each application. Most users rely heavily on the monitor when looking at the digital content.
Using the settings that are configured as the application defaults, color edits are performed based upon operator experience in the screen-printing process. These edits often create an image that looks terrible on screen, but may print quite acceptably, assuming that variables are consistent and standardized within the print process. These variables include mesh count, screen preparation, press settings, etc.
The ICC approach In order to use profiles correctly, we first must understand how color settings can be modified in graphics software. Most graphics applications allow us to define how color is handled. The color settings we select are used to describe how RGB and CMYK content will be created, as well as previewed. We also can define rules that define how content is handled if it does not conform to the color settings we have established. When an image is being previewed onscreen, either the ICC profile that was embedded in the image or the default setting is being applied.
A key point to bring up here is that it´s far easier to alter the color space of the file to match printing conditions than it is to alter printing conditions to match the color space of the file. If we can trust our monitor and its preview by properly configuring the color settings, our subsequent color edits can be more effectively made and trusted.
In the ICC world, we can take the knowledge that the typical content creator uses default settings and use this knowledge to our benefit. Since we know that Photoshop and other applications almost always default to offset printing standards, we will be dealing with a scenario similar to the Photoshop color settings shown in Figure 2.
The vast majority of design files supplied to screen printers come embedded with a default ICC profile for offset printing. To achieve the expected color via screen printing, a custom profile must be generated and applied that matches the standard reproduction parameters of the screen-printing process.
As we move through the list of common CMYK color settings, we see such options as US Sheetfed Coated, PhotoShop 5 Default, US Web Coated SWOP, and so on. Hey, where is the screen-printing option in this list? And what about settings for creating a digital or analog proof? There is a very simple answer in almost all cases: These profile options don´t exist. In order to implement an ICC color-managed workflow, we need to define a CMYK profile that accurately describes the printing scenario. In other words, we have to make one. Once we´ve done so, Photoshop will list the new profile(s) among its standard color settings. Then we can select the new profile and get an accurate preview of our images on screen.
Let´s consider another key concept: The same CMYK values printed to two or more different devices will result in graphics with noticeably different color appearance. This can be seen in Figures 3 and 4. Figure 3 shows a file previewed through the default settings within Photoshop. Figure 4 shows the same file using the soft-proofing capabilities of Photoshop with a profile that reflects the actual printing characteristics delivered by our standard prepress procedures and press settings. This soft-proofing option is accessed by selecting the Proof Setup option from the from the View pull-down menu.
Returning to Figure 4, we see how the image created for offset printing will print on our screen-printing press. Note the color values displayed within the Info Palette in both Figures 3 and 4. The values for the Images are the same, but the preview in Figure 4 is not acceptable. Now compare Figure 5 and Figure 3. Note the preview and the values displayed within the Info Palette. The preview looks very much the same in both images, but the values displayed in the Info Palette are different. We have changed the file in order to compensate for the color-reproduction capabilities of the press.
This preview depicts an on-screen proof of a design file embedded with a default ICC profile for offset printing.
In order to make that change from the customer-supplied color space to our desired color space, we used ICC profiles. The point here is twofold. First, as described previously, the same color on different devices prints differently. Therefore, in order to change the color, we need to change the ingredients. Secondly, once the ingredients have been changed, the on-screen preview can be used to soft proof the change.
In other words, the traditional approach involves trying to alter the device or the process (screenmaking, press, or ink formulation). Conversely, in the ICC scenario, we performed a color-space transformation on the digital file itself, changing the ingredients so it will work under our final printing conditions without requiring that the screen-printing process be altered. This color-space transformation is accomplished using profiles supplied by the customer or designer (source profile) along with the profile that describes our standard printing conditions (destination profile).
The destination profile we used in Figure 4 was created for a screen-printing press and was then used for soft proofing. This profile reflects what results we can expected when specific prepress and printing parameters are maintained. We use this same destination profile to perform a color-space transformation that results in the image shown in Figure 5.
A Photoshop soft proof depicts how the image from Figure 3 would appear if it were screen printed without adjusting its ICC profile for the color-reproduction capabilities of the screen-printing process.
Proofing
Proofs can be created using four or more colors on a single substrate or generated as composite or progressive proofs in which each color is laid down on a separate sheet of clear film. The films can be viewed independently to assess individual colors or assembled in register to be viewed as a full-color composite image. If a proof is supplied with the film or design file, it should be reviewed for size, color, and layout. If a proof will be created internally, it also must be reviewed for size, color, and layout.
The issues Does the proofing system use inks and media that are similar to or consistent with the inks and materials used in screen printing? Is the proof a halftone proof or a continuous-tone proof? If we have a screened (halftone) proof, is the proof supplied using the same line count and screen angles that we will be running on the press? If the proof is a continuous tone or contone proof (an inkjet proof is a typical con-tone proof), was the proofing device calibrated to print like our screen press?
The traditional approach If the answer to any or all of these questions is no (the answer is no virtually all of the time), then there is a problem. The proof will not create a visual match with the image we screen print. Nor will the proof create a visual match to the monitor when the image is previewed at the workstations. This means we will have to alter one or more of the following factors in order to get a match to the proof: digital content, screenmaking procedure, press setup and printing parameters, or ink formulation.
The ICC approach The whole proofing issue can be solved by creating your own proofs internally using inkjet technology and a raster image processor (RIP) that is configurable for proofing. By obtaining or creating an ICC profile of our final print conditions, as well as a profile of our calibrated, optimized inkjet printer, we can quickly and accurately generate color proofs.
In this situation, the source profile will describe your final screen-printing conditions, and the destination profile will represent the inkjet printer´s color space.What we are telling the RIP to do is exactly what we saw in Figure 5. We know the color values have to be changed, but we want the RIP to make the adjustments for us. This approach lets us use one file as the source for all output devices rather than multiple files for multiple devices, which creates confusion.
The objective is to use the RIP´s ICC capabilities to drive the inkjet printer in such a way that it mimics the printing characteristics of the screen-printing press. This results in a color-accurate proof, which should also now conform to our onscreen preview of the file within Photoshop. By using a quality RIP and an inkjet printer, accurate proofs can be created for less than $7.00 per sheet (based on the average cost of hardware, software, and materials).
Any ICC-compliant RIP can be used to generate proofs. However, to achieve the best results, the RIP should provide the following capabilities:
* ability to calibrate for new media, resolution, number of passes, etc.
* ability to load and apply ICC profiles or linked profiles (two or more profiles merged as a single profile)
* ability to create an automated workflow
The ability to calibrate, and subsequently recalibrate, the printer is very important. When the printer drifts (and they all do), or if ink or media is changed, you will no longer be able to print to the standards upon which the profile is based. The use of profiles or linked profiles will ensure that the color-space transformation occurs within the RIP and does not have to be performed manually during prepress.
Workflow automation allows the operators to select specific groups of settings in the various print queues to perform different tasks using the same RIP. The Hot Folder feature offered by the better RIPs is an ideal feature for this process. The operator need only drop the digital files into the watched, or hot, folder and the RIP will automatically RIP and print the digital content. EFI, GMG, ORIS, ONYX, and Wasatch are examples of RIPs used for inkjet proofing. The RIP you use to drive the imagesetter for film output also may have proofing capabilities. Make sure that the features outlined above are included, or you will be disappointed with the results.
Screenmaking and press setup
By this point, the ICC workflow is in place. But to keep this workflow intact, we have to remember one important thing: The ICC profile we are using to transform the file into the final color space is built on a set of parameters that must be standardized. All of the process parameters that come into play from screenmaking through printer setup are part of the process standards. This set of parameters includes screen mesh count and thread diameter, screen tension, emulsion thickness, exposure, squeegee blade selection, and press settings such as off-contact, squeegee pressure and speed, floodbar angle, and other variables. If these conditions aren´t exactly the same as they were when the printing system was profiled, the profile itself will be rendered invalid.
This is essentially the same principle that applies to calibrating an inkjet printer. In screen printing, the calibration starts at screenmaking and includes standardizing every variable that comes into play as the print moves to completion.
Ending pandemonium on press
This is the payoff. If we have correctly implemented an ICC profile-enabled workflow from start to finish, the odds of our print matching our proof are greatly enhanced. Am I claiming that this is a fool-proof process and that we won´t have to color correct on press? Of course not. However, I am saying we will find ourselves doing far fewer color adjustments on press (from squeegee pressure to ink doctoring) if we implement this type of strategy.
As a quick review, we have seen that profiles are used as a form of color communication between your customer, your staff, and all of the devices within the workflow. Preflighting allows the operator to check digital content for color space issues and to identify embedded ICC profiles in the file. In prepress, a final print profile will enable soft proofing of the digital content to ensure that the file will print accurately on press. With these checks and balances in place throughout the workflow, problems can be detected and remedied early. In other words, when the digital content is actually prepared for the screen-printing process instead of for offset printing or another reproduction method, press operators will find less need to make big changes on press in order to achieve accurate color.
Characterizing and Creating an ICC Profile for the Screen-Printing Process
The first step in creating an accurate profile of the screen-printing process is characterizing the printing process. This involves defining the shop standards for screenmaking and press setup so that they are repeatable and the printed results are consistent from run to run. Once this is correct, we can analyze the full color-rendering capabilities of the process and create a profile based on these capabilities.
To create the optimum printing environment, you will need a good, calibrated densitometer. Most densitometers can measure density and tone value increase (dot gain or dot area). Higher-level capabilities include measurement of hue error and grayness, trapping, and print contrast.
Identify the types of substrates you print on. If they are similar to each other, you may only need to develop a single profile. But more than likely, you will need to create a profile for each major substrate type you print.
Next you will need to develop a test target for the press. This target will contain color bars, gradients, color patches, and a series of typical photo images if possible. The color bars will need to include tone range scales from 1-100% in cyan, magenta, yellow, black, red, green, and blue, as well as a three-color grayscale.
To define the cyan, magenta, and yellow values for the three-color grayscale, create an RGB gradient within Photoshop from white to black. Use the US Web Coated CMYK Setting and convert the RGB file to CMYK. Using Photoshop´s eyedropper tool, move the cursor over the image to display the percentages, or ingredients for the creation of a three-color grayscale within the Info Palette. Record these values for the creation of the three-color step wedge. The wedge should show tonal values in at least 10% increments. Do not use black in the three-color step wedge.
A target for determining the total ink limit, or total areas of coverage, will also be required. Chromaticity (www.chromaticity.com) offers a digital file that will assist you in defining this important aspect of print quality.
Next, place an ICC profile target, or set of patches into the layout. Copy various elements of the layout into different locations of the total image area, which will allow you to check for consistency from side to side and top to bottom.
Output the target as film separations, coat and expose screens with the separations, then print the target to the desired density with the completed screens. After printing, check the tone-range scales. Determine what dot size is the smallest you can hold and what is the largest for each of the process colors. Make any changes in screenmaking or press setup that will create consistent appearance and identical measurement values for all colors. Visually evaluate the three-color grayscale for a color cast. Ideally, this grayscale will be a neutral gray. The objective here is to achieve the most saturation or intensity in each of the printing primary colors (CMY) while creating the smoothest reproduction of tonal range.
Adjust your print parameters as needed to achieve an optimal result. If you change the color order, halftone line count or angle, or any other parameter, the process will need to be repeated. Once the press has been optimized for print quality, this setup or configuration will be your press standard.
From this point on, the standard will dictate how the press is run and how production parameters are controlled. Use your densitometer to record the dot values delivered under this print standard, or better yet, measure the results with a spectrophotometer.
Following the procedure recommended by the maker of the ICC profiling software you use (examples include Profile Maker from Gretag MacBeth and Monaco Profiler from X-Rite), also define various ink settings. Ink settings are required in order to define how the printing inks will be used, including how black ink will be used. Typical settings here include a total ink limit (how much of all four inks can be put onto the media), black start and black maximum, and type of black-generation control.
Now you can print your ICC profile targets for the press. Then measure and average a series of targets from various press sheets and locations on the layout to ensure that variations are accounted for among the values you collect.
As a quick overview, the process is as follows:
1. print the target on the calibrated or controlled device
2. measure the printed patches
3. define the ink settings
4. create the profile.
Before plugging your profile into the workflow, take some to evaluate it for accuracy. Create a new test layout with a customer-supplied file, a series of images that you are familiar with (skin tones, food groups, etc.), and a three-color grayscale. Using the newly created profile, transform the original files into the color space supported by your screen-printing process. Next, access the soft-proofing capabilities of Photoshop and review the design for color accuracy. Make sure to check the three-color grayscale to ensure that you have achieved gray balance (neutral gray).
Finally, create the screens and print the job file. Compare the printed piece to the onscreen preview and verify that the process has been optimized. Once the profile has been proven, add it to the list of ICC-compliant profiles in your design software. With the profile in place, color can be more accurately predicted, saving you time and money in your day-to-day operation. This is the true value of the ICC workflow.
Creating Four Color Process Separations in Photoshop
0 komentar Diposkan oleh Unknown di 10/02/2012 08:54:00 PM
Preparing Digital Files for Screen Printing
0 komentar Diposkan oleh Unknown di 10/02/2012 08:54:00 PM
Making other types of artwork fit the screen printing mold
By Mark A. Coudray
One of my favorite quotes regarding technology came from Arthur C. Clarke, who said, "Any sufficiently advanced technology is indistinguishable from magic." I often feel that screen printers using digital prepress are viewed as some sort of magicians who can make any file provided by a customer into a workable graphic. In many cases we can, but learning the right tricks can be a painful process.
Screen printers typically inherit files designed for projects ranging from Web-page building to offset printing. But we rarely see files prepared specifically for our process. So we´re forced to compromise, adjusting the file to get the job out on time while maintaining a reasonable quality level. However, customers are becoming intolerant of compromise, expecting us to maintain the quality of the original design despite the fact that it wasn´t created for screen printing.
Our problems are further compounded by the drive for sales. Unfortunately, our sales people usually don´t understand the nuances of digital art for screen printing, and their view is that we should be happy they got the customer to supply an electronic file in the first place. As they see it, the job of the prepress and production staffs is to produce the final product--no matter what the client furnishes.
Whether we inherit or create a digital file is immaterial. In either case, we must optimize the file for production and prepare it quickly and accurately. I could easily make a short novel out of my experience doing just that. But instead, I want to focus on some of the major factors that differentiate digital artwork for screen printing from graphic files used for other purposes. Among other things, we´ll look at a few real-world approaches to improve the speed, quality, and consistency of our output, regardless of the process or end use for which a file was originally prepared.
The digital workflow
Let´s start with workflow issues. This relates to how quickly the job will move through prepress, how easy the digital file is to work with, and what methods and procedures prepress technicians must use to prepare the file for screen printing. In today´s production environment, speed is the top issue.
The stress on production efficiency and fast turnaround has its roots in the ever-increasing speed of computers. It seems like just yesterday (I think it was, really) when a 100-MHz processor was considered blazingly fast. But according to Moore´s Curve, processing speed will double approximately every 18 months.
This principle has proven remarkably accurate since it was introduced at the end of the 1950s. And following its predictions, by the year 2000, we will be using desktop computers with processing speeds in excess of 800 MHz. (High-end workstations, such as the DEC Alpha, currently run faster than 1000 MHz. But these machines rate a few notches--and dollars--higher than a conventional desktop system.)
Along with faster processors comes software that is more and more complex and feature loaded. Consequently, our customers have developed the expectation that with all this hardware and software power at our disposal, we should be able to turn a job around almost instantly. Don´t we all wish it was so!
The fact is, raw speed does little to streamline prepress or production if the files we receive are improperly prepared for screen printing. And the situations in which files most often fall short include the following: improper placement of graphic elements or trapping, which make it necessary to rework a file extensively images of the wrong resolution for the needed print size color-separation decisions (screen angles, dot gain, etc.) made for lithography or another end use that has little or no bearing on how we use process color in screen printing choices for proofing the digital image that may provide an inaccurate representation of the final screen-printed piece.
While this list may seem extensive, we can take several specific actions to improve the quality of the files we work with and the overall efficiency and accuracy of the process. Setting those heavy traps...
Placement and trapping issues
The first area where digital designs fall apart in terms of their usefulness to the screen printer is in the placement and trapping of graphic elements. Because the images we print may start as digital files prepared for print ads or some other non-screen-printed application, graphic elements within a design may be arranged too tightly to support the more limited resolution capabilities of our process.
Screen printing´s ability to produce high-quality graphics is also influenced by a long list of variables faced by no other printing process, such as mesh selection, screen tension, squeegee parameters, and a wide range of ink chemistries and characteristics. As a result, the graphic elements within a screen-printed design often require heavier trapping than images prepared for lithography or flexography.
If these corrections aren´t made by the customer before you receive the file, it will be up to your own artists and prepress technicians to make the image ready for screen printing. Of course, it also will be up to your staff to determine the actual trapping parameters required based on the type of work you print and the capabilities of your shop.
Incorrect resolution
The resolution issues with screen-printed graphics start as resolution issues with our digital artwork. As noted already, when outside designers create digital graphics for our customers, these files are produced for a variety of uses, but rarely for screen printing. And one of the biggest issues we face is that the graphic files are generally not created with the final size of the screen-printed image in mind.
For example, image files prepared for brochures do not work well when enlarged to produce bus graphics or other large-format displays. This is especially true when the graphic is a bitmap (e.g., TIFF, JPEG, EPS, or similar file format) designed for process-color reproduction. A bitmap may have been scanned at an appropriate resolution to support brochure-size reproduction, but as the size of the graphic increases, the resolution of the bitmap decreases.
To illustrate this concept, imagine a digital image created for use in a brochure. Say this image measures 4 x 6 in. and has a resolution of 300 dpi. Conventional wisdom holds that the resolution of a digital image needs to be roughly double the value of the line count you wish to print. So at its original size, this image could easily be reproduced as a 150-line halftone--an ideal line count for offset printing on a brochure.
Now imagine a customer provided the same image for reproduction as a 12 x 18-in., 85-line/in. screen-printed poster. The image would need to be expanded to three times its original size, which would drop the resolution to 1/3 the original value or 100 dpi. At 100 dpi, the maximum line count you print while maintaining image accuracy is 50 lines/ in., not the 85 lines/in. requested by the customer.
For screen printers, the solution is to interpolate the image. This means relying on software to boost the apparent resolution so that the image contains enough information to be enlarged and support printing at a higher line count. But interpolation really only provides an approximation of the image at a higher resolution, which is a compromise rather than a solution. Fortunately, a new option to correct this problem has recently made its appearance.
Color-separation hurdles
Dot-Gain Profiles
Most CMYK files screen printers receive from customers are created in accordance with lithographic standards and have a dot-gain profile similar to that shown in 1A (left). At lower halftone line counts (50 lines/in. or less), this profile can result in a satisfactory screen print. However, at line counts of 65 lines/in. or more, the dot gain changes to a more typical screen-printing profile (1B, right), and the image must be adjusted in the midtone range to compensate.
With files we receive in CMYK form, all color-separation parameters, including screen angles, dot gain, gray balance, and more, are already established. If the file adheres to lithographic parameters, which is likely the case, you can probably use it as is, provided the line count of the screen-printed graphic is 50 lines/in. or lower. For applications such as large-format and P-O-P display work, lines counts in this range are frequently adequate because the image is viewed at a distance and the dots are large enough to maintain the tonal-range and dot-gain profiles used in litho.
But we begin to run into problems when the line count increases to 65 lines/in. or beyond. Even if we use fine mesh counts and print UV ink, the extreme highlight and shadow dots will become increasing difficult to hold. The dot-gain profile transforms from a traditional, uniform litho profile (Figure 1A) to the more typical screen-print profile (Figure 1B) as the line count increases. The higher the line count, the greater the influence on the dot-gain profile and the bigger the difference in the printed file´s appearance.
To minimize the problems, always ask for both the CMYK and RGB versions of the file. Regardless of how the CMYK file was produced (whether it was created in Photoshop or captured with a high-end scanner), the separation parameters are not easily changed without damaging the color information in the file.
Almost all color-separation programs will discard digital color information when converting from the larger RGB color gamut to the more compressed CMYK gamut. And during this conversion, ink color settings, total ink limit, dot gain, gray balance, and UCR/GCR parameters are also established. But they are established based on standard web offset printing (SWOP) values, and screen printing inks do not match SWOP color parameters. So these values are almost useless.
However, if we can get the RGB file, we can establish the correct separation parameters for your particular application before the conversion to CMYK. This allows us to maintain color continuity with other CMYK pieces created through lithography or other printing methods (Figures 2A-C).
If we cannot obtain the original RGB file, we may be able to convert the CMYK file back to RGB, then apply the correct parameters for screen printing. But the final image will not be as accurate as the original RGB image. The problem is that because black is added to the image during the RGB-to-CMYK conversion, reconverting to RGB will tend to produce too much black, which will be carried over and increased even more when the image is again reconverted to CMYK for the final separations.
Screen printing also requires specific screen angles, line counts, and dot shapes unlike those used for other printing methods. These screen angle sets are one of the most commonly overlooked sources of moiré. For coarse halftones of 50 lines/in. or below, conventional litho angles (Y = 0°, C = 15°, M = 75°, K = 45°) will work if the mesh is a plain weave of 355 thread/in. or more. The dots are large enough that the angular interference of the mesh with the halftone structure is not too much of a problem.
But as the line count gets higher (smaller dots), we must rotate the entire angle set away from the traditional litho angles, primarily because the angles for the yellow and black dots correspond exactly with the weave of the screen mesh and are likely to cause moiré. In most cases, these angles are corrected at the imagesetting stage on the RIP when separations are output to film.
The most common corrected angle set for screen printing is Y = 7.5°, C = 22.5°, M = 82.5°, and K = 52.5°. These values will work for 95% of all screen-printing applications, even with the very fine line counts used by CD decorators. Also note that by using mesh with a lower thread diameter and plain weave, your chances of success increase substantially.
When rotating angles away from the default set used by the imagesetter, be aware that you may need to disable what is known as a screen filter. This is a subprogram or routine used in some RIP programs to help avoid conflicts when many different design elements are placed into a file for output.
Often the placed images will include their own halftone information, which is embedded in the overall design file. This means that each placed file could have different dot shapes, angles, and line counts than those established for the entire graphic. The screen filter makes sure that all of the image elements, including placed files, output with the same angles, dot shapes, and line counts. Unfortunately, such screen filters only apply the standard output angles for lithography and rarely support line counts below 65 lines/in.
To avoid the screen filter, you must open every placed file and make sure the screen angles and halftone information correspond to those used throughout the image. The screen filter must then be disabled on the imagesetter RIP. If you use a service bureau to output your separations, the bureau may need to restart its RIP in order to disable the feature, then turn on the feature when your separations are complete.
Image Adjustment
These images depict the appearance of a CMYK digital graphic before and after adjustment for screen printing. Figure 2A (left) represents the on-screen appearance of the graphic when it is set up for lithographic printing. Figure 2B (center) shows the on-screen appearance after the graphic´s total ink limit and gray-component replacement (GCR) have been adjusted for screen printing. Separations produced from the adjusted file will lead to an accurate printed image (Figure 2C, right).
Proofing digital files
Another challenge we confront is how to proof the images we will be printing. Since screen-printed images at 65 lines/in. or lower have color and halftone characteristics similar to lithographic prints, traditional overlay proofs, Chromalins, or Matchprints will work just fine.
These proofs show halftone dots the way they will appear on the film separations. The physical dot gain you can expect on press is represented by optical dot gain (higher color density) on the proof. Since most proofing systems are designed for offset printing, the standard optical gain is typically about 20%, which means the colors on the proof print will appear 20% darker than on the actual printed piece. Overlay and laminant proofing materials work for offset litho because the dot-gain profile is uniform. Since it is uniform, we can use an optical approximation to represent the actual physical dot gain likely to occur from screen printing.
Screen printers often get into trouble by matching their process-color ink densities to the color printed on the proofing material. This is usually done by matching the color strength of each of the solid CMYK values on the proofing media. In the end, the final screen-printed graphic may end up being 40% darker than the original image because of the 20% proofing adjustment made to the file plus an additional 20% physical gain that naturally occurs on press.
On halftones with line counts above 65 lines/in., the accuracy of our proofs begins to falter due to changing dot-gain profiles. Dot gain when screen printing at finer line counts results in a loss of highlight and shadow information, and more gain in the quarter-tone, mid-tone, and three-quarter-tone areas than the proof can show.
The applications most likely to face these circumstances include fine-line halftones used on compact discs, fine-art prints, and other highly detailed applications that are viewed at close distances. If you attempt to use a conventional analog proof for such images, the highlights and shadows will print too light, and the middle values of the image will be too dark. The overall visual effect will be a very high contrast image with major shifts in neutral colors, such as gray, beige, tan, and brown.
If you have an accurate profile of the gain that occurs on press, you may be able to adjust the proofing system to represent this profile. But even then, many proofing devices lay down the images with a continuous, fine inkjet spray or dye sublimation. Neither of these proof types show the halftone dot structure, which limits their usefulness to screen printers.
The only real solution is to produce the proof image on a screen printing press. If the job in question will be a high-volume run, this is a very viable solution. It´s the only way to be assured that the printed piece will meet client expectations.
Conclusion
To provide our customers with the printed graphics they expect, we have to take control of file preparation, even when they (or their designers) provide the artwork. And one of the first areas we need to focus on is educating our production and sales personnel about what we expect to see in customers´ digital files and why.
We can help our customers produce more useful files in number of ways. For example, we can establish our own internal specifications or guidelines and submit them in writing to our clients. We also can offer workshops and seminars on file preparation and explain why screen printing is different from other printing processes. Finally, after we´ve done our magic and produced the job, we can provide personal feedback to the designers or agencies that created the graphic files, pointing out the problems we discovered and recommending how they can optimize the images for screen printing in the future.
Mostly, however, we remain on our own when it comes to fine-tuning digital artwork for screen printing. So we need to develop standard procedures for checking and correcting (also called preflighting) the files, which will help us uncover problem areas quickly and streamline file preparation. All files should go through this procedure as soon as they arrive--not days or weeks later. This way, if there is an unresolvable issue with the file, we or the customer may be able to correct the problem without sacrificing the job deadline.
By Mark A. Coudray
One of my favorite quotes regarding technology came from Arthur C. Clarke, who said, "Any sufficiently advanced technology is indistinguishable from magic." I often feel that screen printers using digital prepress are viewed as some sort of magicians who can make any file provided by a customer into a workable graphic. In many cases we can, but learning the right tricks can be a painful process.
Screen printers typically inherit files designed for projects ranging from Web-page building to offset printing. But we rarely see files prepared specifically for our process. So we´re forced to compromise, adjusting the file to get the job out on time while maintaining a reasonable quality level. However, customers are becoming intolerant of compromise, expecting us to maintain the quality of the original design despite the fact that it wasn´t created for screen printing.
Our problems are further compounded by the drive for sales. Unfortunately, our sales people usually don´t understand the nuances of digital art for screen printing, and their view is that we should be happy they got the customer to supply an electronic file in the first place. As they see it, the job of the prepress and production staffs is to produce the final product--no matter what the client furnishes.
Whether we inherit or create a digital file is immaterial. In either case, we must optimize the file for production and prepare it quickly and accurately. I could easily make a short novel out of my experience doing just that. But instead, I want to focus on some of the major factors that differentiate digital artwork for screen printing from graphic files used for other purposes. Among other things, we´ll look at a few real-world approaches to improve the speed, quality, and consistency of our output, regardless of the process or end use for which a file was originally prepared.
The digital workflow
Let´s start with workflow issues. This relates to how quickly the job will move through prepress, how easy the digital file is to work with, and what methods and procedures prepress technicians must use to prepare the file for screen printing. In today´s production environment, speed is the top issue.
The stress on production efficiency and fast turnaround has its roots in the ever-increasing speed of computers. It seems like just yesterday (I think it was, really) when a 100-MHz processor was considered blazingly fast. But according to Moore´s Curve, processing speed will double approximately every 18 months.
This principle has proven remarkably accurate since it was introduced at the end of the 1950s. And following its predictions, by the year 2000, we will be using desktop computers with processing speeds in excess of 800 MHz. (High-end workstations, such as the DEC Alpha, currently run faster than 1000 MHz. But these machines rate a few notches--and dollars--higher than a conventional desktop system.)
Along with faster processors comes software that is more and more complex and feature loaded. Consequently, our customers have developed the expectation that with all this hardware and software power at our disposal, we should be able to turn a job around almost instantly. Don´t we all wish it was so!
The fact is, raw speed does little to streamline prepress or production if the files we receive are improperly prepared for screen printing. And the situations in which files most often fall short include the following: improper placement of graphic elements or trapping, which make it necessary to rework a file extensively images of the wrong resolution for the needed print size color-separation decisions (screen angles, dot gain, etc.) made for lithography or another end use that has little or no bearing on how we use process color in screen printing choices for proofing the digital image that may provide an inaccurate representation of the final screen-printed piece.
While this list may seem extensive, we can take several specific actions to improve the quality of the files we work with and the overall efficiency and accuracy of the process. Setting those heavy traps...
Placement and trapping issues
The first area where digital designs fall apart in terms of their usefulness to the screen printer is in the placement and trapping of graphic elements. Because the images we print may start as digital files prepared for print ads or some other non-screen-printed application, graphic elements within a design may be arranged too tightly to support the more limited resolution capabilities of our process.
Screen printing´s ability to produce high-quality graphics is also influenced by a long list of variables faced by no other printing process, such as mesh selection, screen tension, squeegee parameters, and a wide range of ink chemistries and characteristics. As a result, the graphic elements within a screen-printed design often require heavier trapping than images prepared for lithography or flexography.
If these corrections aren´t made by the customer before you receive the file, it will be up to your own artists and prepress technicians to make the image ready for screen printing. Of course, it also will be up to your staff to determine the actual trapping parameters required based on the type of work you print and the capabilities of your shop.
Incorrect resolution
The resolution issues with screen-printed graphics start as resolution issues with our digital artwork. As noted already, when outside designers create digital graphics for our customers, these files are produced for a variety of uses, but rarely for screen printing. And one of the biggest issues we face is that the graphic files are generally not created with the final size of the screen-printed image in mind.
For example, image files prepared for brochures do not work well when enlarged to produce bus graphics or other large-format displays. This is especially true when the graphic is a bitmap (e.g., TIFF, JPEG, EPS, or similar file format) designed for process-color reproduction. A bitmap may have been scanned at an appropriate resolution to support brochure-size reproduction, but as the size of the graphic increases, the resolution of the bitmap decreases.
To illustrate this concept, imagine a digital image created for use in a brochure. Say this image measures 4 x 6 in. and has a resolution of 300 dpi. Conventional wisdom holds that the resolution of a digital image needs to be roughly double the value of the line count you wish to print. So at its original size, this image could easily be reproduced as a 150-line halftone--an ideal line count for offset printing on a brochure.
Now imagine a customer provided the same image for reproduction as a 12 x 18-in., 85-line/in. screen-printed poster. The image would need to be expanded to three times its original size, which would drop the resolution to 1/3 the original value or 100 dpi. At 100 dpi, the maximum line count you print while maintaining image accuracy is 50 lines/ in., not the 85 lines/in. requested by the customer.
For screen printers, the solution is to interpolate the image. This means relying on software to boost the apparent resolution so that the image contains enough information to be enlarged and support printing at a higher line count. But interpolation really only provides an approximation of the image at a higher resolution, which is a compromise rather than a solution. Fortunately, a new option to correct this problem has recently made its appearance.
Color-separation hurdles
Most CMYK files screen printers receive from customers are created in accordance with lithographic standards and have a dot-gain profile similar to that shown in 1A (left). At lower halftone line counts (50 lines/in. or less), this profile can result in a satisfactory screen print. However, at line counts of 65 lines/in. or more, the dot gain changes to a more typical screen-printing profile (1B, right), and the image must be adjusted in the midtone range to compensate.
With files we receive in CMYK form, all color-separation parameters, including screen angles, dot gain, gray balance, and more, are already established. If the file adheres to lithographic parameters, which is likely the case, you can probably use it as is, provided the line count of the screen-printed graphic is 50 lines/in. or lower. For applications such as large-format and P-O-P display work, lines counts in this range are frequently adequate because the image is viewed at a distance and the dots are large enough to maintain the tonal-range and dot-gain profiles used in litho.
But we begin to run into problems when the line count increases to 65 lines/in. or beyond. Even if we use fine mesh counts and print UV ink, the extreme highlight and shadow dots will become increasing difficult to hold. The dot-gain profile transforms from a traditional, uniform litho profile (Figure 1A) to the more typical screen-print profile (Figure 1B) as the line count increases. The higher the line count, the greater the influence on the dot-gain profile and the bigger the difference in the printed file´s appearance.
To minimize the problems, always ask for both the CMYK and RGB versions of the file. Regardless of how the CMYK file was produced (whether it was created in Photoshop or captured with a high-end scanner), the separation parameters are not easily changed without damaging the color information in the file.
Almost all color-separation programs will discard digital color information when converting from the larger RGB color gamut to the more compressed CMYK gamut. And during this conversion, ink color settings, total ink limit, dot gain, gray balance, and UCR/GCR parameters are also established. But they are established based on standard web offset printing (SWOP) values, and screen printing inks do not match SWOP color parameters. So these values are almost useless.
However, if we can get the RGB file, we can establish the correct separation parameters for your particular application before the conversion to CMYK. This allows us to maintain color continuity with other CMYK pieces created through lithography or other printing methods (Figures 2A-C).
If we cannot obtain the original RGB file, we may be able to convert the CMYK file back to RGB, then apply the correct parameters for screen printing. But the final image will not be as accurate as the original RGB image. The problem is that because black is added to the image during the RGB-to-CMYK conversion, reconverting to RGB will tend to produce too much black, which will be carried over and increased even more when the image is again reconverted to CMYK for the final separations.
Screen printing also requires specific screen angles, line counts, and dot shapes unlike those used for other printing methods. These screen angle sets are one of the most commonly overlooked sources of moiré. For coarse halftones of 50 lines/in. or below, conventional litho angles (Y = 0°, C = 15°, M = 75°, K = 45°) will work if the mesh is a plain weave of 355 thread/in. or more. The dots are large enough that the angular interference of the mesh with the halftone structure is not too much of a problem.
But as the line count gets higher (smaller dots), we must rotate the entire angle set away from the traditional litho angles, primarily because the angles for the yellow and black dots correspond exactly with the weave of the screen mesh and are likely to cause moiré. In most cases, these angles are corrected at the imagesetting stage on the RIP when separations are output to film.
The most common corrected angle set for screen printing is Y = 7.5°, C = 22.5°, M = 82.5°, and K = 52.5°. These values will work for 95% of all screen-printing applications, even with the very fine line counts used by CD decorators. Also note that by using mesh with a lower thread diameter and plain weave, your chances of success increase substantially.
When rotating angles away from the default set used by the imagesetter, be aware that you may need to disable what is known as a screen filter. This is a subprogram or routine used in some RIP programs to help avoid conflicts when many different design elements are placed into a file for output.
Often the placed images will include their own halftone information, which is embedded in the overall design file. This means that each placed file could have different dot shapes, angles, and line counts than those established for the entire graphic. The screen filter makes sure that all of the image elements, including placed files, output with the same angles, dot shapes, and line counts. Unfortunately, such screen filters only apply the standard output angles for lithography and rarely support line counts below 65 lines/in.
To avoid the screen filter, you must open every placed file and make sure the screen angles and halftone information correspond to those used throughout the image. The screen filter must then be disabled on the imagesetter RIP. If you use a service bureau to output your separations, the bureau may need to restart its RIP in order to disable the feature, then turn on the feature when your separations are complete.
These images depict the appearance of a CMYK digital graphic before and after adjustment for screen printing. Figure 2A (left) represents the on-screen appearance of the graphic when it is set up for lithographic printing. Figure 2B (center) shows the on-screen appearance after the graphic´s total ink limit and gray-component replacement (GCR) have been adjusted for screen printing. Separations produced from the adjusted file will lead to an accurate printed image (Figure 2C, right).
Proofing digital files
Another challenge we confront is how to proof the images we will be printing. Since screen-printed images at 65 lines/in. or lower have color and halftone characteristics similar to lithographic prints, traditional overlay proofs, Chromalins, or Matchprints will work just fine.
These proofs show halftone dots the way they will appear on the film separations. The physical dot gain you can expect on press is represented by optical dot gain (higher color density) on the proof. Since most proofing systems are designed for offset printing, the standard optical gain is typically about 20%, which means the colors on the proof print will appear 20% darker than on the actual printed piece. Overlay and laminant proofing materials work for offset litho because the dot-gain profile is uniform. Since it is uniform, we can use an optical approximation to represent the actual physical dot gain likely to occur from screen printing.
Screen printers often get into trouble by matching their process-color ink densities to the color printed on the proofing material. This is usually done by matching the color strength of each of the solid CMYK values on the proofing media. In the end, the final screen-printed graphic may end up being 40% darker than the original image because of the 20% proofing adjustment made to the file plus an additional 20% physical gain that naturally occurs on press.
On halftones with line counts above 65 lines/in., the accuracy of our proofs begins to falter due to changing dot-gain profiles. Dot gain when screen printing at finer line counts results in a loss of highlight and shadow information, and more gain in the quarter-tone, mid-tone, and three-quarter-tone areas than the proof can show.
The applications most likely to face these circumstances include fine-line halftones used on compact discs, fine-art prints, and other highly detailed applications that are viewed at close distances. If you attempt to use a conventional analog proof for such images, the highlights and shadows will print too light, and the middle values of the image will be too dark. The overall visual effect will be a very high contrast image with major shifts in neutral colors, such as gray, beige, tan, and brown.
If you have an accurate profile of the gain that occurs on press, you may be able to adjust the proofing system to represent this profile. But even then, many proofing devices lay down the images with a continuous, fine inkjet spray or dye sublimation. Neither of these proof types show the halftone dot structure, which limits their usefulness to screen printers.
The only real solution is to produce the proof image on a screen printing press. If the job in question will be a high-volume run, this is a very viable solution. It´s the only way to be assured that the printed piece will meet client expectations.
Conclusion
To provide our customers with the printed graphics they expect, we have to take control of file preparation, even when they (or their designers) provide the artwork. And one of the first areas we need to focus on is educating our production and sales personnel about what we expect to see in customers´ digital files and why.
We can help our customers produce more useful files in number of ways. For example, we can establish our own internal specifications or guidelines and submit them in writing to our clients. We also can offer workshops and seminars on file preparation and explain why screen printing is different from other printing processes. Finally, after we´ve done our magic and produced the job, we can provide personal feedback to the designers or agencies that created the graphic files, pointing out the problems we discovered and recommending how they can optimize the images for screen printing in the future.
Mostly, however, we remain on our own when it comes to fine-tuning digital artwork for screen printing. So we need to develop standard procedures for checking and correcting (also called preflighting) the files, which will help us uncover problem areas quickly and streamline file preparation. All files should go through this procedure as soon as they arrive--not days or weeks later. This way, if there is an unresolvable issue with the file, we or the customer may be able to correct the problem without sacrificing the job deadline.
Reducing Dot Gain and Improving Tone Range Through Posterization
0 komentar Diposkan oleh Unknown di 10/02/2012 08:52:00 PM
By Mark A. Coudray
Printing halftones involves minimizing dot gain and maintaining a full tonal range. Achieving these two goals becomes more challenging as the halftone line count increases or the substrate becomes less smooth. In screen printing, higher line counts yield progressively higher dot-gain values, and, when combined with poor dot formation, result in tonal-range compression. A loss of tone at each end of the scale flattens the overall image contrast and produces a dark, muddy image.
This article introduces a very useful technique that will help you increase tonal range and improve print contrast and the level of detail within an image. The method is called posterization, and while it may not work in every instance, it is reliable in most cases.
Posterization involves altering the number of grayscale steps in the halftone to minimize tonal compression caused by excessive dot gain. The approach is variable, meaning you can choose how many tonal steps will be represented in your image. You can also preview the effects of posterization before you output film to determine if the number of steps is suitable for your application.
How many levels of gray?
Postscript Levels 1 and 2 support 255 gray levels (162-1) between white and solid values. This means there are 255 steps across the scale. Each step is approximately 0.39%. Very light highlights are the only places such small shifts in tone density are important. The human eye can easily perceive these changes in very light grays, beiges, and flesh tones, and in very light gradations, such as shading of an egg or the transition of light sky blue to the horizon. This shortcoming has been remedied in Postscript Level 3, which supports 4095 tone levels. But only litho printers can bring this level of tonal resolution to their prints.
For screen printers, even 255 steps are overkill. Very few screen shops maintain enough control over their processes to reproduce the subtle differences this level of resolution affords. This lack of control overrides the tonal steps, resulting in contrast reduction.
Improving internal image contrast without sacrificing detail is a more immediate need for screen shops. Fortunately, this need can be fulfilled by judiciously reducing tone through image posterization.
Testing Tones Creating a screen with a range ofposterized gradient patterns is a great way to determine what numberof tonal steps gives you the best prints. This example shows thedifference between a 36- and 255-step grayscale pattern.
How to use posterization
Posterization is nothing more than reducing continuous tone to a specific number of steps. Postscript Levels 1 and 2 posterize at a level of 255 steps. However, you have the power to re-duce the number of steps, thereby increasing the distance to the next tonal value that can be reproduced. For instance, if you posterize at 100 steps, each tonal step will be a 1% increment. A value of 50 will give 2% tonal steps.
To understand how posterization level fits in with the screen-printing process, you have to consider both your prepress and printing capabilities. In prepress, your imagesetter´s output resolution determines the maximum line count you can use. But the higher the line count, the more dot gain you will experience during printing and the fewer tonal steps you can produce.
First, consider the highest line count your imagesetter will support. Assuming a maximum tonal level of 255, you divide the output resolution by 16 to determine the maximum line-count value. For example, if your imagesetter is set for 1200 dpi, the maximum halftone line count would be 1200 ÷ 16 = 75 lines/in. But if the imagesetter is only capable of 600 dpi, the picture changes. In this case, 600 ÷ 16 = 37.5 lines/in., meaning you can´t achieve 255 tonal steps without sacrificing resolution.
If you want to determine the number of tonal steps you can reproduce on film using your current line count, divide the imagesetter resolution by the halftone line count and square the result. So if you have a 600-dpi imagesetter and halftones at 60 lines/in., your film positives would represent 100 tonal steps (600 ÷ 60 = 10, 102 = 100).
Now it´s time to shift focus to how many tonal steps you can actually reproduce on press. The best way to determine this is to conduct a simple test. Begin by creating a test image in Photoshop that consists of a 1 x 14-in. grayscale document. Next, set the foreground color to white and the background color to black. Using the gradient tool, make a blend that starts at 0% and ends at 100%. This will be the gradient that you test print.
Make 12 copies of this image. Next, apply a different number of steps (posterization levels) to each copy. I suggest using squares of whole numbers for each copy (e.g., 25, 36, 49, 64, 81, 100, 132, 144, 169, 196, 225, plus the 255 maximum). Adjust these steps by selecting >Image>Adjust>Posterize and entering one of the values for each copy. You will have 12 different grayscale images. You will also notice that the fewer steps you choose, the more banding that appears in the image. This is what you are after.
The next step is to combine all of the grayscale images into one document and output the file at the line count and halftone angle you normally use. If you know what your dot gain is, apply the correction curve to the document be-fore you output. Compare the finished film to what you see on screen. If your imagesetter is compressing the tone range, you will see banding in the higher level gradients.
In the final step, prepare screens as you normally would and print the image. Again, compare the print to the image on your computer monitor. You will notice that the tone range looks more complete when you posterize at lower levels, and you´ll be able to pick out the individual, discrete tonal steps. The goal is to move up on the tonal steps until the grayscale appears almost continuous. In most cases, this will be in the 64-, 81-, or 100-step range. Anything higher than that is internal resolution that you are not capable of reproducing.
Decreasing dot gain, altering the tone range of the original, or decreasing the halftone line count are the only ways to capture the lost steps. Each approach has its merits--you may end up using all of them. You simply have to understand the limitations and find the compromise that produces the best result with the least visual damage to the image. And you can possibly find a level of posterization that actually improves the way the image looks. That is the goal with this technique. The only real downside is the possibility of banding in very soft, very smooth, long gradients.
Once you have run this test, you will be able to determine which gradient gives you the best reproduction. Then it is simply a matter of posterizing your image to this level while it is in RGB mode. In doing so, you are selectively reducing the amount of information you will be reproducing, while simultaneously increasing the internal contrast of the image. Both of these changes will make the image more forgiving on press and easier to print.
Reaching for the Next Level in Simulated Process
0 komentar Diposkan oleh Unknown di 10/02/2012 08:50:00 PM
Explore how a change in mentality, practice, and process can
ease the transition into simulated-process-color screen printing on
garments.
By Tom Trimingham
A question that I´m commonly asked in e-mails is, "How do I take my current knowledge and experience in screen printing and elevate it to start producing simulated-process prints on dark and colored garments?" Needless to say, this is a hard question to answer in a single e-mail reply. You must manage many variables in art, separations, and printing before you can make the leap, but I am a believer in setting high goals and always reaching for that next level. This column will outline how to bridge the gap between basic multicolor printing and the realm of simulated process printing in an efficient manner with the least amount of stress possible.
Any significant change in a company, especially a manufacturing company that is already comfortable with its process, benefits from an orderly implementation that starts with a change in mentality, then in practice, and finally in overall process. The best results that I have seen in elevating the quality or standards of production come when everyone involved feels some responsibility and ownership in the production process.
The mentality of simulated process
If the first order of change in quality and level of difficulty is a shift in mentality, then it needs to be carefully planned out and implemented in a set of steps that will get everyone involved with the knowledge that they need to accomplish the goal. I have seen big problems when the gauntlet is thrown down and the printing staff is suddenly expected to produce higher quality work of significantly greater difficulty with no additional compensation or appreciation.
Managers and owners can be very tempted to think in black and white and just demand that new levels be reached, but this will commonly be answered with resistance and minimal achievements. That is why it is important to start with the mentality change. Ask yourself, "Who needs to think, train, and act differently for this process to be accomplished, and how can they be motivated?" This is sometimes called the "people factor," and I cannot emphasize enough how a properly motivated group will rocket through a change like this. Some simple ideas on how to motivate people for the move to simulated process:
1. Provide training for your printers and artists, and include rewards/incentives for achievements. Of course, few rewards compare to a monetary one, but sometimes a change in title is even enough. Silly as it may sound, a new title of master printer or senior artist can do wonders in motivation when the money isn´t available.
2. Set a realistic timetable for necessary training and tasks to be completed. Factor in some practice and training downtime for each area: artwork prep, separations, screenmaking, press setup, and printing production.
3. Find a role model or mentor—a person who has handled this level of printing before—and use that individual as a resource and motivator. Everyone should believe that they, too, can accomplish the task.
Wait until everyone is on board for the challenge before you venture out onto the practice stage. As you move through the more difficult steps in a higher level of printing, it is important to review the mentality and morale of the people involved and make sure they are willing to hang in through the learning curve. People commonly agree to things in a meeting, but then when the going gets tough, they revert back to old habits or get turned off quickly. So stay tuned to your group´s morale, and let them know the achievement is one that everyone will be proud of in the end.
The practice of simulated process
I understand that the typical motivation for a company to move up into simulated-process printing is customer demand for specific artwork, but the ideal situation is not to attempt a whole new process from scratch on a deadline-driven customer order. Doing so is setting up a situation for serious and expensive problems.
A better approach is to carefully move through each area of the screen-printing process with a practice piece of artwork that will allow for a fair amount of time along the way for the learning curve. The downside to this is that practicing doesn´t generate money. Nevertheless, I have found that practicing simulated-process printing is essential to developing consistency and catching problems before the scrapped shirts start piling up at the end of the dryer. The proper walk-through of simulated-process practice starts in the art department, then moves to the screen department, and finishes at the press.
The art department´s role
Proper training in the art department will stave off most of the potential headaches with simulated process work. The artwork you print will only be as good as the set of separations used to create the screens, so the approach your artists take to produce designs needs to be systematic and controlled. Most of the problems tend to be out of the artist´s hands when a customer provides the artwork, so it´s best to make your first foray into simulated process printing with artwork that´s been created to work well with this method.
A design I created for the wildlife market was constructed specifically for use in simulated-process printing (Figure 1). The simplest way to create artwork like this is to begin with a controlled palette of colors that you select as you illustrate. In this case, I used a palette of eight colors that I blended to produce the final artwork (Figure 2). Some artists hate to force the design process within a palette such as this, but it really pays off when it comes time to separate and print the artwork. An art department making the switch to simulated process for the first time should start by defining a palette of inks. These inks are then simulated in Photoshop as color palettes for the art department to use when designing garment graphics. These colors can be saved as swatches that every artist can refer to when creating new designs. In the beginning, your shop will have its hands full with art development and separation, so relying on swatches to help control color use will save your staff time and hassle.
Figure 1 Designing for Simulated-Process Printing
If you want to effectively create art for simulated-process printing, work from a palette of standard colors that work well in simulated process and concentrate on developing images with good edge quality and blending between colors.
Another issue when it comes to training your artists is to have them create artwork that has definitive edge quality and blending. The edge quality of an image is determined by how well the contrast of the outlines in an image work to border the areas of color. Whenever possible, it is ideal to have a sharper, more defined edge quality to an image that will be separated for simulated process. Fuzzy edges are problematic, and the trouble is compounded by the reproduction through a halftone screen. A good way to control this is to use black outlines to define all of the shape edges in the design. They don´t have to be thick lines, and in the case of my design, I used a black hairline as rough border to confine the shapes and colored areas within (Figure 3).
The blends in a design created in house should be controlled to shift cleanly from one swatch color to another and/or drop in value as they fade into a dark garment. Gradual color blends that overlap each other without a solid opacity may produce hues that are difficult to separate and can cause color-matching problems when on press. Always remember that overlapping colors on the monitor have different hues than what your inks will reproduce.
Figure 2 The Color Palette in Use
Eight colors were used in this graphic for simulated-process printing.
The final steps of art preparation and separation are accomplished simultaneously. The preparation stage of the art should be minimal, assuming the art was created correctly in house using a predetermined color palette. On the other hand, if the customer supplied the art, you will truly never know what you are going to get. It´s common for customer-supplied artwork to have way too many colors, blends that are not definitive to two separate colors, and poor edge quality. In these cases, be sure you work with the customer to have the art recreated so that it will reproduce well—or make it crystal clear that what they see on paper can´t possibly represent what the final shirt will look like. If everything is wrong with the art (poor quality edges, too many colors, etc.), then try to insist on a recreation before moving the art to the separation stage. Doing so ensures that the final work will be of higher quality. No one ends up happy with poorly printed shirts.
Separating for simulated process can be a very artistic process in itself. I have found the best, most consis-tent results by splitting the artwork into channels in Photoshop and then resetting the colors in the channels to match the art for a clear picture of the final product. You can use any number of paths to split the artwork into channels. One of these methods is to use plug-in separation software for Photoshop that does it for you. The plug-in´s success depends largely on how well the artwork is prepped and designed.
Figure 3 Edge Quality
The better the graphic´s edge quality, the easier it is to separate. The stencil often magnifies poor edge quality on press.
Another method that is more meticulous and time consuming (but very accurate) is to carefully extract each color as a curve and then define it as a spot-color channel. These spot channels are then recombined in order into one file to simulate what the final print will look like (Figure 4). In this manner, the artwork is essentially separated and rebuilt at the same time. This approach also gives the clearest picture of the final print´s appearance. The task of pulling each spot channel takes significant training and a careful, detail-oriented eye to accomplish well, but the results can be simply awesome. An effective way to train an artist (or non-artist) to handle spot channels is to bring in a consultant who has significant experience. A third party can walk artists through the practice of prepping and separating with the least amount of press downtime.
In a tough spot, it´s really a smart move to send a difficult file out to have it professionally separated so that the films will be the best possible reproductions. The money that this costs will pay off with less press downtime and fewer scrapped shirts (or prevent the loss of the whole order). The goal is to move into simulated-process screen printing with confidence that the art and separations are the best that they can be.
Figure 4 The Combined Image
Using Photoshop´s Curves tool to isolate colors into spot-color channels can be tedious, but the method can yield stunning results. Here, the eight colors used in the design are separated into individual channels and recombined to emulate what the design will look like on a black T-shirt.
Simulated process in the screen room
The big difference in changing up from regular spot-color printing into simulated process is that you´ll be printing finer lines and halftone dots. A good way to practice is to simply print a variety of halftone dots in solid blocks from 0-100% and in graduated blends to make sure you´re selecting screens that can hold the dots. I always advise companies that are just starting out to avoid really fine dots. Newcomers will find it was easier to hold and print a 42-line/in. halftone than a 55-line/in. one. Remember that you´ll want to have at least four threads of mesh per dot, so a, 42-line halftone would require an 180-thread/in. mesh. Check the tension of each screen with a tension meter. It´s more important for the screens to be similar in tension than all high tension, but having a tension above 18 N/cm really helps control variables such as screen stretch and color peel-up onto the back of the next screen.
Other things to consider and watch are the exposure system and the washout to make sure you´re getting a really good, clean border on the dots in your stencil. Look at the dots through a loupe and check for nice clean edges. If your emulsion looks ripped at the edges or distorted, you will have to adjust the exposure time and possibly the pressure of the washout system. The shirt will never be any better than the films—and subsequently the screens—so it´s essential that all of your hard-earned work in the art department is properly reproduced on screen.
The final print
Carefully managing all of the other areas in the workflow really takes the pressure off of the printers. The main difference between simulated printing and conventional spot-color printing is what I call skim-rather-than-smash printing. Using tight screens with fine details requires some practice with the press. Start by going through this checklist and make adjustments where necessary:
1. Make sure everything is level (platens, screens in down position, and squeegees if you´re using an automatic press).
2. Check your squeegee blades and sharpen them if necessary. I recommend a 70-durometer squeegee or a triple-durometer 60/90/60 for most simulated-process printing.
3. If you´re running a manual press, make sure you practice printing some halftone gradations so that you can be sure you´re not crushing out your tonal range. Make your body move like a machine, and try to keep even pressure and speed from side to side and through the length of the stroke.
4. Test your inks. Inks commonly need viscosity reduction for halftone printing. Just be careful you don´t adjust the opacity by breaking them down too much. A couple of percentage points in viscosity change go a long way.
5. Find the brightest, low-tack (won´t stick in the screen) white available to create a good underbase.
6. Test your flash, and flash just enough to gel the ink and avoid pick up on the next screens.
7. Watch for registration shifts that may indicate the press isn´t aligned properly or that a poorly stretched screen is causing excessive screen stretch.
8. Control the pressure! This is often the biggest problem. Remember that detailed printing is more about the careful release of the ink from the screen than smashing it through the mesh. Pressure control will help control dot gain. I´ve seen manual press operators who can print as good a shirt as an automatic press when they carefully control their squeegee pressure.
The final result
Take time to evaluate your simulated-process results and document the problems, as well as the things that are working. Recording the process is a good final step for ensuring that you´ll be able to repeat it for the orders that follow. Don´t be discouraged if the first print on the press doesn´t look right. Try to determine right away whether a color change or art change is the problem. Often a small color change will give good results when the artwork is prepped and separated on target. Switching from spot-color printing to simulated-process printing can seem like a really big hurdle, but with right mindset, careful preparation, and diligent execution, it can lead to garment prints that will make your company proud and your customers ecstatic.
By Tom Trimingham
A question that I´m commonly asked in e-mails is, "How do I take my current knowledge and experience in screen printing and elevate it to start producing simulated-process prints on dark and colored garments?" Needless to say, this is a hard question to answer in a single e-mail reply. You must manage many variables in art, separations, and printing before you can make the leap, but I am a believer in setting high goals and always reaching for that next level. This column will outline how to bridge the gap between basic multicolor printing and the realm of simulated process printing in an efficient manner with the least amount of stress possible.
Any significant change in a company, especially a manufacturing company that is already comfortable with its process, benefits from an orderly implementation that starts with a change in mentality, then in practice, and finally in overall process. The best results that I have seen in elevating the quality or standards of production come when everyone involved feels some responsibility and ownership in the production process.
The mentality of simulated process
If the first order of change in quality and level of difficulty is a shift in mentality, then it needs to be carefully planned out and implemented in a set of steps that will get everyone involved with the knowledge that they need to accomplish the goal. I have seen big problems when the gauntlet is thrown down and the printing staff is suddenly expected to produce higher quality work of significantly greater difficulty with no additional compensation or appreciation.
Managers and owners can be very tempted to think in black and white and just demand that new levels be reached, but this will commonly be answered with resistance and minimal achievements. That is why it is important to start with the mentality change. Ask yourself, "Who needs to think, train, and act differently for this process to be accomplished, and how can they be motivated?" This is sometimes called the "people factor," and I cannot emphasize enough how a properly motivated group will rocket through a change like this. Some simple ideas on how to motivate people for the move to simulated process:
1. Provide training for your printers and artists, and include rewards/incentives for achievements. Of course, few rewards compare to a monetary one, but sometimes a change in title is even enough. Silly as it may sound, a new title of master printer or senior artist can do wonders in motivation when the money isn´t available.
2. Set a realistic timetable for necessary training and tasks to be completed. Factor in some practice and training downtime for each area: artwork prep, separations, screenmaking, press setup, and printing production.
3. Find a role model or mentor—a person who has handled this level of printing before—and use that individual as a resource and motivator. Everyone should believe that they, too, can accomplish the task.
Wait until everyone is on board for the challenge before you venture out onto the practice stage. As you move through the more difficult steps in a higher level of printing, it is important to review the mentality and morale of the people involved and make sure they are willing to hang in through the learning curve. People commonly agree to things in a meeting, but then when the going gets tough, they revert back to old habits or get turned off quickly. So stay tuned to your group´s morale, and let them know the achievement is one that everyone will be proud of in the end.
The practice of simulated process
I understand that the typical motivation for a company to move up into simulated-process printing is customer demand for specific artwork, but the ideal situation is not to attempt a whole new process from scratch on a deadline-driven customer order. Doing so is setting up a situation for serious and expensive problems.
A better approach is to carefully move through each area of the screen-printing process with a practice piece of artwork that will allow for a fair amount of time along the way for the learning curve. The downside to this is that practicing doesn´t generate money. Nevertheless, I have found that practicing simulated-process printing is essential to developing consistency and catching problems before the scrapped shirts start piling up at the end of the dryer. The proper walk-through of simulated-process practice starts in the art department, then moves to the screen department, and finishes at the press.
The art department´s role
Proper training in the art department will stave off most of the potential headaches with simulated process work. The artwork you print will only be as good as the set of separations used to create the screens, so the approach your artists take to produce designs needs to be systematic and controlled. Most of the problems tend to be out of the artist´s hands when a customer provides the artwork, so it´s best to make your first foray into simulated process printing with artwork that´s been created to work well with this method.
A design I created for the wildlife market was constructed specifically for use in simulated-process printing (Figure 1). The simplest way to create artwork like this is to begin with a controlled palette of colors that you select as you illustrate. In this case, I used a palette of eight colors that I blended to produce the final artwork (Figure 2). Some artists hate to force the design process within a palette such as this, but it really pays off when it comes time to separate and print the artwork. An art department making the switch to simulated process for the first time should start by defining a palette of inks. These inks are then simulated in Photoshop as color palettes for the art department to use when designing garment graphics. These colors can be saved as swatches that every artist can refer to when creating new designs. In the beginning, your shop will have its hands full with art development and separation, so relying on swatches to help control color use will save your staff time and hassle.
If you want to effectively create art for simulated-process printing, work from a palette of standard colors that work well in simulated process and concentrate on developing images with good edge quality and blending between colors.
Another issue when it comes to training your artists is to have them create artwork that has definitive edge quality and blending. The edge quality of an image is determined by how well the contrast of the outlines in an image work to border the areas of color. Whenever possible, it is ideal to have a sharper, more defined edge quality to an image that will be separated for simulated process. Fuzzy edges are problematic, and the trouble is compounded by the reproduction through a halftone screen. A good way to control this is to use black outlines to define all of the shape edges in the design. They don´t have to be thick lines, and in the case of my design, I used a black hairline as rough border to confine the shapes and colored areas within (Figure 3).
The blends in a design created in house should be controlled to shift cleanly from one swatch color to another and/or drop in value as they fade into a dark garment. Gradual color blends that overlap each other without a solid opacity may produce hues that are difficult to separate and can cause color-matching problems when on press. Always remember that overlapping colors on the monitor have different hues than what your inks will reproduce.
Eight colors were used in this graphic for simulated-process printing.
The final steps of art preparation and separation are accomplished simultaneously. The preparation stage of the art should be minimal, assuming the art was created correctly in house using a predetermined color palette. On the other hand, if the customer supplied the art, you will truly never know what you are going to get. It´s common for customer-supplied artwork to have way too many colors, blends that are not definitive to two separate colors, and poor edge quality. In these cases, be sure you work with the customer to have the art recreated so that it will reproduce well—or make it crystal clear that what they see on paper can´t possibly represent what the final shirt will look like. If everything is wrong with the art (poor quality edges, too many colors, etc.), then try to insist on a recreation before moving the art to the separation stage. Doing so ensures that the final work will be of higher quality. No one ends up happy with poorly printed shirts.
Separating for simulated process can be a very artistic process in itself. I have found the best, most consis-tent results by splitting the artwork into channels in Photoshop and then resetting the colors in the channels to match the art for a clear picture of the final product. You can use any number of paths to split the artwork into channels. One of these methods is to use plug-in separation software for Photoshop that does it for you. The plug-in´s success depends largely on how well the artwork is prepped and designed.
The better the graphic´s edge quality, the easier it is to separate. The stencil often magnifies poor edge quality on press.
Another method that is more meticulous and time consuming (but very accurate) is to carefully extract each color as a curve and then define it as a spot-color channel. These spot channels are then recombined in order into one file to simulate what the final print will look like (Figure 4). In this manner, the artwork is essentially separated and rebuilt at the same time. This approach also gives the clearest picture of the final print´s appearance. The task of pulling each spot channel takes significant training and a careful, detail-oriented eye to accomplish well, but the results can be simply awesome. An effective way to train an artist (or non-artist) to handle spot channels is to bring in a consultant who has significant experience. A third party can walk artists through the practice of prepping and separating with the least amount of press downtime.
In a tough spot, it´s really a smart move to send a difficult file out to have it professionally separated so that the films will be the best possible reproductions. The money that this costs will pay off with less press downtime and fewer scrapped shirts (or prevent the loss of the whole order). The goal is to move into simulated-process screen printing with confidence that the art and separations are the best that they can be.
Using Photoshop´s Curves tool to isolate colors into spot-color channels can be tedious, but the method can yield stunning results. Here, the eight colors used in the design are separated into individual channels and recombined to emulate what the design will look like on a black T-shirt.
Simulated process in the screen room
The big difference in changing up from regular spot-color printing into simulated process is that you´ll be printing finer lines and halftone dots. A good way to practice is to simply print a variety of halftone dots in solid blocks from 0-100% and in graduated blends to make sure you´re selecting screens that can hold the dots. I always advise companies that are just starting out to avoid really fine dots. Newcomers will find it was easier to hold and print a 42-line/in. halftone than a 55-line/in. one. Remember that you´ll want to have at least four threads of mesh per dot, so a, 42-line halftone would require an 180-thread/in. mesh. Check the tension of each screen with a tension meter. It´s more important for the screens to be similar in tension than all high tension, but having a tension above 18 N/cm really helps control variables such as screen stretch and color peel-up onto the back of the next screen.
Other things to consider and watch are the exposure system and the washout to make sure you´re getting a really good, clean border on the dots in your stencil. Look at the dots through a loupe and check for nice clean edges. If your emulsion looks ripped at the edges or distorted, you will have to adjust the exposure time and possibly the pressure of the washout system. The shirt will never be any better than the films—and subsequently the screens—so it´s essential that all of your hard-earned work in the art department is properly reproduced on screen.
The final print
Carefully managing all of the other areas in the workflow really takes the pressure off of the printers. The main difference between simulated printing and conventional spot-color printing is what I call skim-rather-than-smash printing. Using tight screens with fine details requires some practice with the press. Start by going through this checklist and make adjustments where necessary:
1. Make sure everything is level (platens, screens in down position, and squeegees if you´re using an automatic press).
2. Check your squeegee blades and sharpen them if necessary. I recommend a 70-durometer squeegee or a triple-durometer 60/90/60 for most simulated-process printing.
3. If you´re running a manual press, make sure you practice printing some halftone gradations so that you can be sure you´re not crushing out your tonal range. Make your body move like a machine, and try to keep even pressure and speed from side to side and through the length of the stroke.
4. Test your inks. Inks commonly need viscosity reduction for halftone printing. Just be careful you don´t adjust the opacity by breaking them down too much. A couple of percentage points in viscosity change go a long way.
5. Find the brightest, low-tack (won´t stick in the screen) white available to create a good underbase.
6. Test your flash, and flash just enough to gel the ink and avoid pick up on the next screens.
7. Watch for registration shifts that may indicate the press isn´t aligned properly or that a poorly stretched screen is causing excessive screen stretch.
8. Control the pressure! This is often the biggest problem. Remember that detailed printing is more about the careful release of the ink from the screen than smashing it through the mesh. Pressure control will help control dot gain. I´ve seen manual press operators who can print as good a shirt as an automatic press when they carefully control their squeegee pressure.
The final result
Take time to evaluate your simulated-process results and document the problems, as well as the things that are working. Recording the process is a good final step for ensuring that you´ll be able to repeat it for the orders that follow. Don´t be discouraged if the first print on the press doesn´t look right. Try to determine right away whether a color change or art change is the problem. Often a small color change will give good results when the artwork is prepped and separated on target. Switching from spot-color printing to simulated-process printing can seem like a really big hurdle, but with right mindset, careful preparation, and diligent execution, it can lead to garment prints that will make your company proud and your customers ecstatic.
The profit potential in single-color garment designs is a lot
greater than you may realize. This month, Triming-ham describes how to
add visual impact, extra value, and a higher price tag to your one-color
work.
By Tom Trimingham
Can a T-shirt printed with just a single color really be worth more than one decorated with a dozen? Today’s market for printed apparel says it certainly can.
I discovered this trend, much to my surprise, during a recent online investigation of retail prices for screen-printed shirts. A careful review of the top ten, highest priced, best-selling shirts showed how fashion trends, mixed with innovative garments, niche-specific branding, and unexpected designs, produce high-end shirts that can command hefty prices. And all of it is possible by using only one screen from the shop floor.
If everyone were able to obtain such results so easily, we’d all be in the business of printing single-color designs on T-shirts. So here’s the question we must answer: What makes one garment designed with a single-color graphic worth more than $50 at retail while another sells for a fraction of that?
Perceived value
The designs that grab the premium retail prices are those that convey a high perceived value. This concept, according to my findings, is more important than how many colors are present in a garment graphic—and it’s ultimately what allows one printed T-shirt to command a price ten times higher than another, even though both are produced the same way.
I created a simple spreadsheet to aid in my research. On it, I listed the number of colors on the printed T-shirts and the amounts charged to direct consumers. My review revealed that, in many cases, no correlation existed between the number of colors in a print and the end product’s cost. The shirts ranged from less than $5 to more than $55 apiece, and the expensive garments actually seemed to have designs with fewer colors than the cheapest shirts, which typically sported eight-color prints.
Such a scenario contradicts conventional wisdom, but it’s commonplace in fashion marketing, where manufacturers strive to produce goods that are similar to what is currently popular, yet are original at the same time. We can mimic large-scale, popular brands—but with a high-production mindset—and present our original work to a percentage of our more fashionable clients, who will pay more to look a little trendy.
The plan
Planning for fashion marketing requires an important shift in mentality. It must be genuine and authentic to work with any consistency in sales. Let’s start with what I call the pre-objection stage. Visualize the objections that clients will have to higher costs and deal with the issues before you implement your marketing plan. You won’t be able to predict every objection, because printers and artists tend not to think from the customer’s view.
A printer’s first thought usually is that a one-color print is a one-color print and represents the same amount of production time. Why should it be worth more?
An artist’s view commonly is that the design is just another simple, distressed piece for athletic wear. How could it be worth so much more than another one?
The customer’s viewpoint comes primarily from a financial standpoint: “This is what I budgeted for these shirts.” Or you might hear, “This is what my customers are willing to pay.”
You must educate customers by explaining why the prints are worth more. Demonstrate how the customers can persuade their clients to accept the values and benefits of the new garments. You need to believe in and be excited about the value in the garment to really sell it. Such a situation is very similar to an artist talking to potential buyers about a painting—breaking down the message and explaining how it fits into what other people are buying.
You may wish to address some production details once you’ve shown excitement and comfort in selling trendy fashion prints to clients at a higher price. The details you provide about the production end complement a hands-on approach to selling and can aid you tremendously in the negotiation of value.
Very successful brands that sell high-priced, single-color prints consistently use the following collection of elements to form a foundation: ownership of the garment, high-impact artwork, surprising printing location and technique, and a refusal of limitations. Let’s examine the specifics of each.
Ownership of the garment
According to my research, the shirts that maintained a great following at a high price point all featured elements that indicated the garments were original. You can achieve the same results in a variety of ways.
Private label This costs 25-75 cents per shirt, depending on volume and the necessary service steps. You can purchase garments without tags and heat-transfer a label onto the shirt. Check with your local garment mill to see what is available. Unique locations for labels can be appealing as a valued look, such as on a sleeve hem, a wraparound on the neck or sleeve fabric on the inside, side-seam tags, and even metal, flock, or leather heat-applied or sewn-in brand identifiers. Clients who are willing to pay a premium need to see that the shirt looks different from a typical garment that anyone can buy. This step directly supports the feeling of exclusiveness.
Custom dyes and color effects The highest priced shirts on my list were ones that had custom colors and wash effects, including grinding and/or distressing to the shirts’ seams. Many of these effects are easy and cost-effective to recreate, especially in a shop that’s equipped with an inexpensive washer and dryer. You won’t find a must-do list here. Some shirts featured several special effects, and others had very little. The idea is to differentiate the shirt from others on the market and increase the softness and vintage look.
The softer, the better Research shows that special effects that increase the perceived softness of a garment increase its value. Can we wash or process a low-cost garment to magnify its softness? Fabric softeners and washing techniques can do the trick and add a special effect at the same time. Enzyme wash is a popular one. Only use unscented products.
The fit that your market demands Some shirts just don’t fit well. More expensive shirts tend to consist of spandex (even if they don’t say it on the tags) in order to conform to the wearer’s body and create the feel of a better fit. Fashion-forward clients are very interested in how a garment fits. Make sure you know its dimensions. What’s the in style right now? Look into long shirts with conforming shapes, thinner necks, and shoulder hems. Some manufacturers are surprisingly open to customizing garments—even in smaller quantities.
High-impact artwork
High-impact artwork makes a lasting impression on the viewer. A visually striking piece can be simple and harmonious or really edgy—something that creates a visceral reaction, such as a piece I created for a popular mixed martial arts fighter (Figure 1).
The Impact of Artwork: The type of reaction you want from
buyers plays a huge role in the way you design your garment graphics. I
went for a hard-edged look with this creation.
This style of art is popular in that niche and worked well visually because of its hand-crafted appeal and dark imagery. Clients either like or loathe this style, but they rarely ignore it. If you want to sell high-value pieces or create your own brands, then find an artist who can develop a trendy piece with a dramatically original, hand-crafted feel—one that fits your target niche. If the process of realizing a high profit margin on a one-color print requires an investment on your part, spend the money on a talented artist. Be sure to review work samples, and always be upfront about payment and expectations.
The use of uncommon techniques is another way add value to artwork. Unconventional halftone patterns and vintage designs that echo a garment treatment give a premium feel to a simple garment (Figure 2).
Uncommon Techniques: Using unique halftone patterns, overlays, and textures adds tremendous appeal to otherwise simple designs.
The gritty look and what I like to call the kindergarten look are popular these days with designs that are drawn completely by hand and purposefully made to look loose and playful (Figure 3).
Playful Designs: One-color designs that are manipulated to look informal or hand-drawn are popular right now.
Designs created in watercolor, pastels, charcoal, ink brush, and multimedia can produce surprising combinations and lend an iconic, rustic, and vaguely medieval look to the artwork—even in just one color.
Earning appreciation for high-priced artwork sometimes means informing the client about the attention and effort that you’ve put into the design. Have you ever heard someone at a museum say “What’s the big deal with that Picasso painting? My daughter has been drawing stuff like that since kindergarten!” The point is that Picasso’s cubist works directly confronted the realistic paintings of others to create a different effect on the viewer. Having the understanding of what the artist is trying to accomplish adds value, whether or not you like a design. The value to the viewer stems from in the education behind the effort. T-shirt art won’t hang next to a Picasso in a museum, but knowing the terminology and being able to communicate it during a garment sale can help to establish a more significant price for your work.
An artist’s attention to detail helps define the difference between artwork of lower quality and artwork of high value. A graphic design intended for a high-fashion market should have an increased level of research and detail care attached to it. You can even sell very simple artwork at a higher cost when you use a design that’s researched, design-specific, and tested to be the best. The proper communication of the amount of care and development you assign to a project can increase its price.
Surprising location and technique
Successful marketing companies know that everyone loves surprises. Variety adds visual interest, and the unexpected often creates a demand where there pre-viously was none. For example, take a heraldic crest design, distress it, and dull it so that it barely appears on the shirt. Then include a different, tribal-looking print merged across it (Figure 4).
Clash and Contrast: You can enhance the appeal of a
single-color garment decoration by combining dissimilar elements in the
design and placing the print in an unconventional location.
The contrast in styles creates visual tension and makes the shirt much more interesting than one that features only a simple tribal print. The added detail also ties into perceived value. For a final touch, print the design in unique location so that it wraps over the shoulder and sleeve of the shirt with the tribal image cutting across it diagonally. You now have an edgy design in an unexpected location and image clash that justifies a higher cost. Other ways to surprise and create interest with a single color are:
• repeated images that form patterns all over large areas of the shirt
• tattoo-type print locations on garments with images that collage together to form image clashes
• washed-out prints that fall off of the sides, collar, seams, or sleeves of the garment
• inks with glitters, textures, and differ- ent finishes (such as gel, suede, etc.) that contrast with the imagery or feel of the garment
• combinations of halftones and patterns to break up a single color in rhythms of different hues on the shirt
The proper mindset
Mentality is what separates the shops that consistently create high-priced, single-color prints from the bulk of other garment screen printers. They don’t believe in limitations, which creates an environment where they’re willing to reconstruct their production environment based on the needs of the print rather than always adjusting the design to fit the shop’s limitations. They make custom platens, screens, and squeegees when they need to print off of the edge of the shirt and all over one sleeve. They install washing machines and have thermally active labels produced for shirts that need custom tag prints with an enzyme wash and a grinding on the collar. And rather than adjust the art and force the print and shirt to conform, these screen printers opt for the difficult path that leads to a challenging print that’s more original.
The details of this single-color, high-price mentality may sound like a lot of artsy talk and fluff, but the customers who demand these prints are willing to pay for a higher level of service. They don’t care that the shirt is one color when they see examples and get excited about the possibilities. Not every order for single-color T-shirts pays big bucks, but if you make a priority of exciting your customers with new possibilities, you’ll be able to reap the rewards of a high-profit, one-color print.
By Tom Trimingham
Can a T-shirt printed with just a single color really be worth more than one decorated with a dozen? Today’s market for printed apparel says it certainly can.
I discovered this trend, much to my surprise, during a recent online investigation of retail prices for screen-printed shirts. A careful review of the top ten, highest priced, best-selling shirts showed how fashion trends, mixed with innovative garments, niche-specific branding, and unexpected designs, produce high-end shirts that can command hefty prices. And all of it is possible by using only one screen from the shop floor.
If everyone were able to obtain such results so easily, we’d all be in the business of printing single-color designs on T-shirts. So here’s the question we must answer: What makes one garment designed with a single-color graphic worth more than $50 at retail while another sells for a fraction of that?
Perceived value
The designs that grab the premium retail prices are those that convey a high perceived value. This concept, according to my findings, is more important than how many colors are present in a garment graphic—and it’s ultimately what allows one printed T-shirt to command a price ten times higher than another, even though both are produced the same way.
I created a simple spreadsheet to aid in my research. On it, I listed the number of colors on the printed T-shirts and the amounts charged to direct consumers. My review revealed that, in many cases, no correlation existed between the number of colors in a print and the end product’s cost. The shirts ranged from less than $5 to more than $55 apiece, and the expensive garments actually seemed to have designs with fewer colors than the cheapest shirts, which typically sported eight-color prints.
Such a scenario contradicts conventional wisdom, but it’s commonplace in fashion marketing, where manufacturers strive to produce goods that are similar to what is currently popular, yet are original at the same time. We can mimic large-scale, popular brands—but with a high-production mindset—and present our original work to a percentage of our more fashionable clients, who will pay more to look a little trendy.
The plan
Planning for fashion marketing requires an important shift in mentality. It must be genuine and authentic to work with any consistency in sales. Let’s start with what I call the pre-objection stage. Visualize the objections that clients will have to higher costs and deal with the issues before you implement your marketing plan. You won’t be able to predict every objection, because printers and artists tend not to think from the customer’s view.
A printer’s first thought usually is that a one-color print is a one-color print and represents the same amount of production time. Why should it be worth more?
An artist’s view commonly is that the design is just another simple, distressed piece for athletic wear. How could it be worth so much more than another one?
The customer’s viewpoint comes primarily from a financial standpoint: “This is what I budgeted for these shirts.” Or you might hear, “This is what my customers are willing to pay.”
You must educate customers by explaining why the prints are worth more. Demonstrate how the customers can persuade their clients to accept the values and benefits of the new garments. You need to believe in and be excited about the value in the garment to really sell it. Such a situation is very similar to an artist talking to potential buyers about a painting—breaking down the message and explaining how it fits into what other people are buying.
You may wish to address some production details once you’ve shown excitement and comfort in selling trendy fashion prints to clients at a higher price. The details you provide about the production end complement a hands-on approach to selling and can aid you tremendously in the negotiation of value.
Very successful brands that sell high-priced, single-color prints consistently use the following collection of elements to form a foundation: ownership of the garment, high-impact artwork, surprising printing location and technique, and a refusal of limitations. Let’s examine the specifics of each.
Ownership of the garment
According to my research, the shirts that maintained a great following at a high price point all featured elements that indicated the garments were original. You can achieve the same results in a variety of ways.
Private label This costs 25-75 cents per shirt, depending on volume and the necessary service steps. You can purchase garments without tags and heat-transfer a label onto the shirt. Check with your local garment mill to see what is available. Unique locations for labels can be appealing as a valued look, such as on a sleeve hem, a wraparound on the neck or sleeve fabric on the inside, side-seam tags, and even metal, flock, or leather heat-applied or sewn-in brand identifiers. Clients who are willing to pay a premium need to see that the shirt looks different from a typical garment that anyone can buy. This step directly supports the feeling of exclusiveness.
Custom dyes and color effects The highest priced shirts on my list were ones that had custom colors and wash effects, including grinding and/or distressing to the shirts’ seams. Many of these effects are easy and cost-effective to recreate, especially in a shop that’s equipped with an inexpensive washer and dryer. You won’t find a must-do list here. Some shirts featured several special effects, and others had very little. The idea is to differentiate the shirt from others on the market and increase the softness and vintage look.
The softer, the better Research shows that special effects that increase the perceived softness of a garment increase its value. Can we wash or process a low-cost garment to magnify its softness? Fabric softeners and washing techniques can do the trick and add a special effect at the same time. Enzyme wash is a popular one. Only use unscented products.
The fit that your market demands Some shirts just don’t fit well. More expensive shirts tend to consist of spandex (even if they don’t say it on the tags) in order to conform to the wearer’s body and create the feel of a better fit. Fashion-forward clients are very interested in how a garment fits. Make sure you know its dimensions. What’s the in style right now? Look into long shirts with conforming shapes, thinner necks, and shoulder hems. Some manufacturers are surprisingly open to customizing garments—even in smaller quantities.
High-impact artwork
High-impact artwork makes a lasting impression on the viewer. A visually striking piece can be simple and harmonious or really edgy—something that creates a visceral reaction, such as a piece I created for a popular mixed martial arts fighter (Figure 1).
This style of art is popular in that niche and worked well visually because of its hand-crafted appeal and dark imagery. Clients either like or loathe this style, but they rarely ignore it. If you want to sell high-value pieces or create your own brands, then find an artist who can develop a trendy piece with a dramatically original, hand-crafted feel—one that fits your target niche. If the process of realizing a high profit margin on a one-color print requires an investment on your part, spend the money on a talented artist. Be sure to review work samples, and always be upfront about payment and expectations.
The use of uncommon techniques is another way add value to artwork. Unconventional halftone patterns and vintage designs that echo a garment treatment give a premium feel to a simple garment (Figure 2).
The gritty look and what I like to call the kindergarten look are popular these days with designs that are drawn completely by hand and purposefully made to look loose and playful (Figure 3).
Designs created in watercolor, pastels, charcoal, ink brush, and multimedia can produce surprising combinations and lend an iconic, rustic, and vaguely medieval look to the artwork—even in just one color.
Earning appreciation for high-priced artwork sometimes means informing the client about the attention and effort that you’ve put into the design. Have you ever heard someone at a museum say “What’s the big deal with that Picasso painting? My daughter has been drawing stuff like that since kindergarten!” The point is that Picasso’s cubist works directly confronted the realistic paintings of others to create a different effect on the viewer. Having the understanding of what the artist is trying to accomplish adds value, whether or not you like a design. The value to the viewer stems from in the education behind the effort. T-shirt art won’t hang next to a Picasso in a museum, but knowing the terminology and being able to communicate it during a garment sale can help to establish a more significant price for your work.
An artist’s attention to detail helps define the difference between artwork of lower quality and artwork of high value. A graphic design intended for a high-fashion market should have an increased level of research and detail care attached to it. You can even sell very simple artwork at a higher cost when you use a design that’s researched, design-specific, and tested to be the best. The proper communication of the amount of care and development you assign to a project can increase its price.
Surprising location and technique
Successful marketing companies know that everyone loves surprises. Variety adds visual interest, and the unexpected often creates a demand where there pre-viously was none. For example, take a heraldic crest design, distress it, and dull it so that it barely appears on the shirt. Then include a different, tribal-looking print merged across it (Figure 4).
The contrast in styles creates visual tension and makes the shirt much more interesting than one that features only a simple tribal print. The added detail also ties into perceived value. For a final touch, print the design in unique location so that it wraps over the shoulder and sleeve of the shirt with the tribal image cutting across it diagonally. You now have an edgy design in an unexpected location and image clash that justifies a higher cost. Other ways to surprise and create interest with a single color are:
• repeated images that form patterns all over large areas of the shirt
• tattoo-type print locations on garments with images that collage together to form image clashes
• washed-out prints that fall off of the sides, collar, seams, or sleeves of the garment
• inks with glitters, textures, and differ- ent finishes (such as gel, suede, etc.) that contrast with the imagery or feel of the garment
• combinations of halftones and patterns to break up a single color in rhythms of different hues on the shirt
The proper mindset
Mentality is what separates the shops that consistently create high-priced, single-color prints from the bulk of other garment screen printers. They don’t believe in limitations, which creates an environment where they’re willing to reconstruct their production environment based on the needs of the print rather than always adjusting the design to fit the shop’s limitations. They make custom platens, screens, and squeegees when they need to print off of the edge of the shirt and all over one sleeve. They install washing machines and have thermally active labels produced for shirts that need custom tag prints with an enzyme wash and a grinding on the collar. And rather than adjust the art and force the print and shirt to conform, these screen printers opt for the difficult path that leads to a challenging print that’s more original.
The details of this single-color, high-price mentality may sound like a lot of artsy talk and fluff, but the customers who demand these prints are willing to pay for a higher level of service. They don’t care that the shirt is one color when they see examples and get excited about the possibilities. Not every order for single-color T-shirts pays big bucks, but if you make a priority of exciting your customers with new possibilities, you’ll be able to reap the rewards of a high-profit, one-color print.
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