Layer Blend Modes
Perched near the top-left corner of the Layers panel is an unlabeled menu of blend modes, which control how pixels on different layers interact with one another. (Unless you change it, this menu is set to Normal.) For example, when layers overlap, the top one can either block the bottom one completely, or the colors on those layers can blend together in some way (these effects, and many more, are shown in Figure 7-7). You control exactly how the colors blend together by using blend modes.
This section covers how to use layer blend modes, but you can find other blend-mode menus all over the place in Photoshop:
In the Layer Style dialog box, where you can add effects like drop shadows, glows, and so on (Layer Styles).
In some filters’ dialog boxes and in most filters’ Blending Options dialog box, which you get by using smart filters (see Chapter 15).
In the Fade dialog box, which you can access via Edit→Fade right after you run a filter (see the box on Fading Filters) or after applying most of the adjustments in the Image→Adjustments menu.
In the Options bar when you’re using a tool you can paint with, like the Brush, Paint Bucket, Healing Brush, Pencil, Clone Stamp, History Brush, Gradient, Blur, Sharpen, and Smudge tools, and the shape tools (when they’re set to Pixel drawing mode).
In the Calculations (Combining Channels) and Apply Image dialog boxes. (To learn how to combine two images using the Apply Image command, which lets you pick the channel Photoshop uses to ...