I'll bet there's a tutorial on this somewhere on the web, but I can't find it. I'm trying to stack several images together. In order to see underlying layers, I need to remove varying shades of black from each layer. Rather than using the magic wand tool, I'd like to turn black to tranparent varying on intensity ( 100% K = 0% opacity, 50% K = 50% opacity, etc...). Ideas? Suggestions? Dirty jokes?