Simplifying Color Separations

Pulling colors from artwork so that they can be reproduced on screen-printed apparel doesn’t need to be complicated. In fact, the whole process of breaking a design down into printable sections of color shouldn’t require years of experience, custom software, or intense mathematical formulas. The best way to separate a design for screen printing is often the simplest, keeping as much of the feel of the original design as possible in the final print.

Pulling colors from artwork so that they can be reproduced on screen-printed apparel doesn’t need to be complicated. In fact, the whole process of breaking a design down into printable sections of color shouldn’t require years of experience, custom software, or intense mathematical formulas. The best way to separate a design for screen printing is often the simplest, keeping as much of the feel of the original design as possible in the final print.

Avoid trying to create extra colors using strange combinations of inks or applying semi-transparent overprints to detailed existing prints unless absolutely necessary. Over-involved or design-specific separation practices can be counterproductive to developing an easy-to-repeat process that will consistently produce good results without a lot of on-press headaches.

A good goal for a screen-printing production artist is to reproduce art in a way that a wide variety of press operators could handle and that customers would still be excited to receive. Developing a set of guidelines that plan out the separation method in advance will help you perform separation tasks quickly without losing control of quality. The guidelines should cover things like properly adjusting the artwork, defining color spaces, and pulling the positives for each color using an extraction method. Processing artwork using a defined set of steps can dramatically speed up your separation work without sacrificing detail or consistency.

A quick note: As with most rules that apply to artwork, my suggestions for simplifying separations will not work on every design. When you consider the tremendous variation of hues, color-saturation levels, value ranges, and image modes available, there will always be a small number of designs that will not fit any standardization process. The methods discussed below should provide a path that will allow you to separate a large percentage of designs with better results.

Advertisement

Resolution and Color Pollution
The two biggest issues that compromise the majority of pre-separation artwork are insufficient resolution and color pollution (unexpected colors appearing where you don’t want them as you prepare the separations). Resolution is the king of culprits, but color pollution is often right behind in terms of the problems it causes. Depending on the design, you can often find yourself with a catch-22 decision: Should you try to separate a low-resolution file the client provided, or spend time rebuilding it in the hope it will separate more cleanly? Rebuilding the artwork will give you a clean, finished set of separations that you know will work. (Figure 1, at left, illustrates the type of improvement that can be gained.) But the downside of doing extensive re-engineering and retouching is that it is becoming harder and harder to get clients to pay for it.

One certainty that every screen printer should consider: Producing separations from artwork that will not create a good finished product may save money in the short term, but it’s not a good business plan. It’s better to have a difficult conversation with clients to explain how the art needs to be redone and why. It shows them that you care about the products you’re producing for them and demonstrates your dedication to quality. Even if clients are reluctant to pay for such art services outright, spending the time to fix the problem rather than jury-rig a low-resolution image will help you in the long run. Develop a sales aid like the one in Figure 2, at right, showing the fuzzy-edged print that a customer can expect from a low-resolution file versus a clean print that will result from artwork that has been recreated; this can often solve the issue without a lot of debate.

The color-pollution issue, on the other hand, can sneak up on you. Occasionally, a file will come in that has been resampled from a low-resolution image that had been previously compressed. When you go to scale the image back up, you’ll find other colors randomly sprinkled into solid areas (Figure 3, left). This problem is hard to see without a really close inspection of the art. More often, you notice it when the job goes to separation.

Color pollution can also be caused by hue variations that are present in a lot of naturally colored items such as flesh, wood, plants, water, and metal. These surfaces aren’t really solid in color – they are composed of different colors or reflections that, when combined, form an overall color tone. But on closer inspection (or separation), you realize they are composed of many different colors.

Fortunately, there is a quick fix that will prevent you from having a lot of extra colors in a design while making the separations considerably simpler and more predictable. Using Photoshop, select all of the areas in the image that have a similar overall color tone. Create a new layer and then copy and paste the elements there. Next, use the Hue/Saturation/Lightness dialog box and check the “Colorize” option for these copied pieces only on this layer. The initial color tone will look strange, so you will need to play with the three settings to dial in the right hue and saturation to make the color look natural. Once you’re finished, you will have effectively “color crushed” the pollution out of that area of the design. If the results look too harsh, you can adjust this layer’s opacity setting to blend it with the original file, which will help to minimize the color pollution.

Defining the Color Spaces in the Design
This sounds like a fancy process, but the goal is straightforward: to gauge the fundamental color needs of the design. When you first analyze an image and how to go about preparing it for screen printing, the natural inclination is to think about how many colors will be required. The additional trick is to know whether any of the colors that you’re estimating for the job will be difficult to reproduce. For example:

Advertisement

• Out-of-gamut hues (such as hot neon colors);
• Images with a lot of neutral colors with temperature changes (such as warm and cold grays);
• And unrealistic gradients (for instance, yellow fading into purple without looking brown).

Designs with challenges such as these are good to red flag from the beginning. Discuss the problems with clients to see how closely the color spaces need to be adhered to or if the designs can be effectively crunched down to simpler sets of colors.

Separating Using the Extraction Method
The more complex a design, the more effective it is to take the separations one piece at a time and work through them in a logical progression. Even with very colorful pieces that have a multitude of blends and interacting colors, you can build them up slowly, one screen at a time, in Photoshop. I call the process color extraction, and it’s the simplest way to handle complex artwork.

Imagine a flame design, with three colors comprising a blend that you want to appear smooth in the final print, stacked on top of one another like a pyramid. Now picture what the pyramid would look like if you were to view it from the side, at the print level. With all three colors and a white underbase stacked on top of one another, as in Figure 4 on the right, the print could become very heavy and the layers of ink likely to mash together. Using a traditional separation approach, it might be difficult to get the right amount of yellow, orange, and red so that the colors blend properly. Typically, you would get a solid red underneath and too much yellow on top that would tend to gain and cover the orange.

Color extraction involves a different approach in which a “squeezed” version of the overprint colors are knocked out of the colors underneath. The process is commonly done to avoid the dreaded bulletproof-print effect, but it’s actually a fantastic separation method to use all the time.

Here’s how it would work for the flame design. First, you would extract out the orange separation. Once you’ve defined this middle color in the blend in a Photoshop color channel, duplicate it and squeeze (or compress) the black and white points in the Values setting. (In the old days of photographic process cameras, we would have called this making a “skinny” of the color.) Then take this modified channel copy and extract it from the red, repeat the same steps for the red channel, and then knock both colors out of the yellow channel entirely.

Advertisement

The process works a little like dominoes, using an easy-to-define color with good details to extract out the other surrounding or overprint colors that may be difficult to isolate as quickly. The twin benefits of the approach are an easier way to separate difficult images and final prints that use less ink and feel softer (see Figure 5 on the left).

Remember, when handling complicated designs, it’s easy to overthink the separation process and make it more difficult than it needs to be. By simplifying things and sticking with a well-defined process, you’ll usually get better results on the final print in less time.