Subtract and Divide Blending Modes in AE CS4
http://library.creativecow.net/rollas... Ben Rollason demonstrates how to do subtract and divide blending modes in Adobe After Effects CS4 and below. CS5 now features the subtract and divide blending modes, which makes this process much easier, but if you are using an earlier version, Ben's tutorial enables you to accomplish these same effects with just a few simple steps.
Ben suggests that now that people are creating new CS5 projects with built-in subtract and divide blending modes, there may be a call to 'retrofit' these options to earlier versions.