Uses for the (New??) Subtract and Divide Blend Modes

Photoshop Top 40, Feature #25: Selection Calculations

Press the Shift key to add to a selection. Press Alt (or Option) to subtract and Shift+Alt (Shift+Opt) to find an intersection. Helpfully, these tricks apply to layers, channels, and paths. They're a power user's dream.

Channels & Masks Lesson 10: Using Calculations in Photoshop

The Scent of Stamina