For some time now, I've been using three kinds of blending modes in my digital paintings: an underlying Normal layer where I paint only local colors, a Multiply layer on top of that for shades and shadows, and an "Add (Glow)" layer (a.k.a. Linear Dodge in Photoshop) for highlights. It's possible to paint everything in a single normal layer, but then you'd have to figure out for yourself how the colors change as light and shade strike them. I've discovered that it's possible to reverse-engineer a photograph to see how light and shade affect local colors. For this demonstration, I'm going to use a photo called Alex stock 27 by Random-acts-stock. The first thing to do is to try to extract the local colors from this photo. I can't do this with 100% reliability, so the best I can hope for is a reasonably accurate guess. By doing some digital painting as well as blending mode manipulation, I was able to come up with the following image. As you can see, I kind of fudged the details