Simulated Process Color Separations for Screen Printing – Part One

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Part One of a two part article. Click here to read Part Two.
Printing detailed, photorealistic images on dark shirts has always been the ultimate goal of most garment screen printers. Yes, the bread and butter is in basic images (for most printers), but there is nothing like lifting the last screen and seeing a masterpiece on the garment. It can bring tears to your eyes! But…… there is nothing like lifting the last screen and breaking down in tears because the image just doesn’t look right and you have no idea what to do next…..AND, the customer is due to approve the print in ten minutes. This article will detail how to do very respectable color separations and photorealistic prints on dark shirts. I use the word “respectable” because no matter how much time I spend going over the steps, there is still a learning curve. All of us who do high-end printing have learned through years of trial and error and through many failures. If you follow these steps you will be on your way to creating high-end prints. You just need to remember that with each job, you will gain knowledge about what is important and what is not. While this article will deal with some color theory, it is designed more as a primer to help the average printer achieve results in a short time period without having to go back to college art class. What is Simulated Process Color? This term has been around for a long time. In simple terms, it is a method of printing photorealistic images without using the standard CMYK separations. I like to say the image looks like “process color” (CMYK), smells like process color but it isn’t process color. In fact “simulated process color” uses off-the-shelf inks that are standard opacity plastisols printed on top of high opacity plastisol as a base or “underbase" (see Figure 1). Why is it so hard? It is hard because again, we are trying to use standard inks and make the image print like process colors. We are also printing on a base of white and trying to be faithful to the original artwork. A tough task. One of the “secrets” of great simulated process color is that the print needs to stand on it’s own. This means that while it might be faithful to the majority of the original art, it should be bright and detailed. How many times have you seen the “original artwork” when you view the coveted Golden Image winners at the SGIA show? Never. I think you might be shocked at the difference on some prints. Others, might match the original but what you DON’T see are the three or four attempts and screen re-burns it took to get to that point. I know this sounds negative, but it is the reality of working with so many variables like shirt composition, ink opacities, poor original artwork and worst of all, high customer expectations. OK, enough of this negative talk. Let’s get down to specifics. We will look at artwork requirements, image adjustment and color separations, screen, ink, press setup and printing requirements. This article was originally written in 2005 using Photoshop 7.0. Don't worry. None of the steps have changed. Photoshop of cours is the program of choice for image manipulation and color separations. All steps here will work with any version of Photoshop. While it is nice to know how to do these things and this article deals with a LOT of items like getting the image looking good before you separate it - many artists just don't want to remember all the steps and have opted for plugins for Photoshop that do this with the push of a button. Check out my plugin T-Seps here if you want to see all these steps happen in a flash before your eyes. Yes, this is a blatant plug. But you will learn a lot in this article about the process, prepping artwork and more. This article is a must read if you plan to do higher end photorealistic work. This one is sometimes a real joke. How many times have you gotten a low quality JPG image from a web graphic and been expected to us it as the artwork. Better yet, they give you the CD label and want it on a shirt. When you see a magnificent print that has detail and edge definition, it came from a magnificent original that had detail and edge definition. If you take the 72dpi image that is the size of a wallet photo and blow it up to 200 dpi, you will have a “soft” 200 dpi image. I deal with sample files from customers and students every day and I have to always ask, is this all you have to work with? The answer is always, that’s it!
Figure 1 - Click on images to see larger version.

Figure 1 – Click on images to see larger version. Use the BACK button to return to article.

Figure 2

Figure 2

Your original image should be from a good graphic, photograph, illustration, or image created in a drawing program like Corel, Illustrator or Photoshop, that is the final image size at a resolution of 200 to 250 dpi. Yes, it can be lower resolution but hard edges will be softer (see Figure 2).

Photoshop Setup
We will be using Adobe Photoshop to do the separations and it then stands to reason that we will use Photoshop to do the pre-separation image adjustment. In order to not make this article an entire book, the following steps assume that you have done a monitor calibration (detailed in your Photoshop manual). Also, in order to preview the individual alpha channels (separations) correctly you must tell Photoshop to display the image with the proper dot gain. Go to Edit/Color Settings and under Working Space, set Spot to 30%. Under RGB, set the monitor profile to Apple RGB (see Figure 3).

Image Adjustment Improve contrast
The best images for dark shirts have good contrast. If the image has what appears to be “black areas,” make sure they ARE dead black by checking them with the Info Palette (Window/Show Info). Dead black is “0” levels of RGB (see Figure 4). It is also helpful to improve the contrast by applying an “S” Tone Curve adjustment (Image/Adjustments/Curves) (see Figure 5).

Photoshop has a feature called Auto Color (Image/Adjustments/Auto Color). Auto Color improves contrast and color saturation (see Figure 6). Very nice!

Poor quality JPG’s
If the image did come from a low quality JPG image, the “boxes” that are created by the JPG routine averaging the color in areas will be GREATLY enhanced when you do color separations. If your image does have blocky areas, you might actually have to soften these areas before color separating (see Figure 7). Photoshop has routines designed to improve/enhance JPG images and there are inexpensive programs on the web called JPG Enhancement programs.

Keep edges hard
If you created the image in a vector program, make sure to NOT use Anti-Aliasing when importing the image. The edges will become soft and this will show up in the final print (see Figure 8).
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Figure 7

Figure 8

Figure 8

Figure 3

Figure 3

Figure 4

Figure 4

Figure 5

Figure 5

Figure 6

Figure 6

Use Unsharp Masking
Most images supplied by the customer need to be sharpened. I recently worked with images from a “well known theme park company” who supplied images for cartoon characters to a printer in Mexico City. All of the images were very soft and needed major “unsharp masking” applied to them. The printer assumed that the customer knew what they were doing and I had to work hard to convince them that typical artists don’t really know what a screener needs. I rarely work on a design without first seeing if the image needs Unsharp Masking (Filter/Sharpen/Unsharp Mask). OK, the name seems wrong, but Unsharp Masking sharpens areas of high contrast. Start with settings of Amount 150%, Pixel Radius of 1 and Threshold of 5 (see Figure 9). Then take the Amount slider all the way to 500%. You will be SHOCKED at the improvement to some images. Others will get very grainy over 200%. Be bold here.

Two Versions of Artwork Needed
If the image is going on black or dark shirt colors you will need TWO versions of the file. One version is the normal image with white as the “canvas” or background. The second version of the artwork has black around the image in the canvas areas (see Figure 10). This is called a “masked” file and will be used for the underbase and highlight. I spent a lot of time trying to explain why you need two versions of the artwork. The simple answer is that to pull the colors from the image, you MUST have the background or “canvas” white. Otherwise you would not be able to create the “color” portions of the separations. If the image is on a “shirt” color, the shirt color really has nothing to do with the color separations. In order to make an underbase of an image, the canvas areas MUST be black because you will be making a grayscale of this image and it will be inverted. You don’t want to print a solid block of white around the image. Just buy into it and trust me on this.

The easy way to create two versions of the image is to build the image in Layers in Photoshop and then create one version with a black background and another with a white background (see Figure 11). Flatten the image and you are ready to separate. Another method is to airbrush around the image with black or use the Magic Wand and select the areas around the image and fill these areas with black. If at all possible, YOU WANT TO GET THE ORIGINAL ARTWORK IN LAYERS from the customer if possible so you have more control over these things. Color Separations Are Critical
Figure 9

Figure 9

Figure 10

Figure 10

Figure 11

Figure 11

I like to joke that if the seps are done correctly, the printing is easy! Although this article details how to do the separations, there are a number of automated color separation programs on the market that do this for you. Many of these programs do a great job and will save you hours of trial and error. In fact most go through hundreds of complex moves that would be impossible to teach in a short article. Even if you have an automated color separation program I think it important that you understand the basic steps so you will be able to know about the inner workings of this process. Keep in mind that color separators (myself included) who learned this process using filters in a camera (years ago!), often like to use each of the Red, Green and Blue channels of the RGB image and each of the Cyan, Magenta, Yellow and Black channels of a traditional CMYK image to “build” an image using all or parts of those channels for each color separation when creating simulated process separations.

If you have a lot of experience, you can look at the individual RGB and CMYK channels and determine if it in fact has the color information you need. As an example, the Black channel of a CMYK image might be good enough (probably too weak) for the black plate of your separations. The cyan channel probably has the “blue” areas. The yellow and red channels might have information that can be used to make browns, etc.

Also, experience separators and the automated separation programs use the Photoshop Calculations command to combine, exclude, subtract and do other manipulation of the individual RGB channels (I will touch on this briefly later). This requires a lot of work, much trial and error and a good experience level (can you say “lots of failures?”). With that in mind, this article will detail the easiest and quickest method to use and one that requires much less experience. Contrary to what you might think, the original image must be in RGB mode. You should have the image open and the Channels Palette visible when doing the color separations.

Underbase and Highlight White
Images that go on dark shirts need an underbase of white ink (generally NOT a solid image), and a Highlight White that is typically printed last. Yes, you need two whites but this is a must.

Creating Highlight White
Open the “masked version” of the artwork (black around the image). Using Color Range (Select/Color Range) select just the white in the design with the eyedropper. Use the Fuzziness slider to determine how much white you want. Remember, this just needs to be the whitest parts of the image. It is a judgement call (see Figure 12). Too much and you will mute down the colors when you print the image. Make sure Invert is checked. Say OK to the Color Range window. Save this selection as a channel (Select/Save Selection). Name this channel Highlight White by double-clicking on the Channel Header (see Figure 13).
Figure 12

Figure 12

Figure 13

Figure 13

This is Part One of a two part article. Click here to read Part Two.
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