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Predicting and Managing Dot Gain

(December 2011) posted on Wed Jan 11, 2012

The advice shared here will help you anticipate the dot gain you’ll experience in your garment-printing work and minimize its ne


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By Screen Printing's Solution Sourcebook

Art
The best way to adjust dot gain visually in Adobe Photoshop depends on your color-separation method. One of the easiest ways is to load each separation selection into an individual alpha channel with the layer options tuned to echo each ink color (Figure 3). You then can view the channels and overlay them onto each other to see how they’ll interact. This doesn’t give you a true example of the final print, because of the opacity and the interplay of the hue shifts that may occur, but it can come close enough to catch any major problems.

After you load a separation set into channels, you can adjust and view the dot gain that is likely to occur by opening each channel and then using Photoshop’s curves menu. You want to push the midtone of the curve diagonally toward the black point of the menu. This will cause the image to get darker and lose tonal range quickly as the values start to flatten and lose division between levels of brightness. Watch for a visible change in tonal value that approximates what you see in your test prints and the effect that this tonal shift has on your image’s clarity. The example in Figure 4 shows the extreme level of dot gain that may occur by pushing the curves menu too far. Lightening the value of the underbase reveals how the image can be damaged.



The lessons that you learn from these curves adjustments should affirm the results you saw on your test prints. You can expect value increases throughout your separation set that are similar to what you saw with your test file. If you desire an even higher level of precision in determining levels of likely dot gain, you can record the input and output levels of the adjustment curve after you adjust your original test file to echo the printed sample as closely as possible. Then you could save this curve adjustment in the curves menu and load it when you wish to adjust a separation channel that has the same halftone line count, uses the same ink, and will be printed on the same garment type as the test sample. This method should provide you with a very predicable adjustment tool for standard dot gain using a controlled set of variables.


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