The most common color-separation problems often have very simple solutions. Read on to find out how you can overcome the issues you commonly face.
A trap is even easier in Photoshop. I just copy the underbase channel and then modify it with the Curves menu or use the Magic Wand to select just the outside area (this works on some images that have clean edges). I can then quickly contract the selection and add a stroke or delete the outside to make it slightly smaller.
1: No digital proof of the file made This is it—the number one mistake in separations. The digital proof is the foundation we use to catch all of the other mistakes. Taking the time to rebuild a file as a Photoshop channel-separation set makes the rest of the top five mistakes obvious to some degree (Figure 5). If you get the hang of recreating your separation sets in Photoshop as channels with the ink colors set up, you will improve your success rate dramatically.
Solution: Take your projected shirt color, make an alpha channel that is solid, and use this color as a barrier to then create your other separation channels after it in the print order in which they are supposed to print. If you already do this and still have some of the other issues crop up, then it is important for you to slow down and really look at what the trouble areas look like in the digital proof. Potential issues on press manifest themselves early in digital proofs.
What you see in a proof may not look exactly like what you’ll see go wrong on press, but you’ll almost always find a valuable clue. For example, a slight line of the underbase will show or the overprint color will look dull. These are trapping or density issues. The gradients may not blend well or the colors may look blocky. In my experience the final file rarely looks a lot better in detail than the digital proof. If the proof looks great in Photoshop, then you have a really good start—and it’s likely that you will avoid dealing with the top five mistakes in a separation set when you go to press.
Tom Trimingham has worked in the screen-printing industry for more than 15 years as an artist, art director, industry consultant, and head of R&D for some of the nation's largest screen printers. He is an award-winning illustrator, designer, and author of more than 45 articles on graphics for screen printing. He can be reached through his Website, www.art2screen.com.
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