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The Top Five Mistakes in Separations

(August 2009) posted on Mon Aug 10, 2009

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.


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One method of creating an underbase for a dark garment is to make the background around the original design black and then create a duplicate of the image in Adobe Photoshop. The image is then converted to L*a*b* color and the lightness channel is used to create the underbase by copying and then pasting this channel into the original channel separation set and then inverting it. This channel is then used as a working underbase. The problem is that deep saturated colors, like a fire-engine red or a royal blue, average out through the lightness channel as a medium/dark gray, which only gives them a 40-50% underbase using this method (Figure 2). If this separation set were printed with such a weak underbase, the final result would look dull and lifeless and could even shift colors completely.

Solution: There is no simple road to dealing with this issue other than getting to know your inks and what they need to be printed on to create bright, vibrant images. If your inkset requires a 100% white underprint to create a brilliant red, then you’ll need to boost this area in the underbase. My favorite way of dealing with this issue is to use a color-range tool in Photoshop and select the most saturated of the red color in the image (or whatever color that needs to have the underbase adjusted underneath) and use a low fuzziness inside of this tool to avoid adjusting too much of the graduated colors in the underbase—just the brightest areas. Once I make this selection, I then switch to the underbase channel and use the Curves menu to bump the density of just this area in the underbase to compensate for the color saturation. This approach has the added benefit of finding all of the areas in an image that have this deep, saturated color so you won’t miss any spots.


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