With a digital portrait that I want to retouch in software, I’ve discovered the best way to evaluate my subject’s complexion is to view the portrait in black-and-white. Now, my final step in touching up a portrait is to open Adobe Photoshop’s Channels palette, and evaluate just the Green channel. This monochrome version boldly highlights any blemishes or wrinkles I may have missed.

—Reader Tip from Trudy Zeitsinger, Portland, ME