If the subject of your image is radically brighter or darker than its background, you’ll want to sit up and pay attention to this section. While blend modes are pretty powerful in their own right (and several of ’em can instantly pulverize a white or black background), another set of blending options in the Layer Style dialog box (Layer Styles) can eat backgrounds for lunch—nondestructively!
Photoshop gives you a few different ways to open the Layer Style dialog box (Figure 8-18). Once you’ve activated the Image layer you want to work with, open the dialog box using one of the following methods:
Double-click the layer’s thumbnail in the Layers panel.
Click the fx button at the bottom of the Layers panel and then choose Blending Options.
Choose Layer→Layer Style→Blending Options.
The Blending sliders won’t work on a locked Background layer; you have to double-click the layer first to unlock it.
At the bottom of the Layer Style dialog box lie two pairs of sliders (they look like triangles): one set for the This Layer bar and another for the Underlying Layer bar, shown in Figure 8-18. Each slider lets you make parts of your image transparent based on the brightness value of the pixels. The left-hand sliders represent the shadows (blacks) in the image, and the right-hand ones represent the highlights (whites). To affect the currently active layer, tweak the This Layer slider (you’ll learn about the Underlying Layer slider in a moment).