Back in the old days, InfiniD had a neat little feature that when you rendered an alpha channel it was very easy to use it for compositing images in Photoshop. If you had something that was semi transparent , it would create shades of gray to be able to select transparency fairly easily and strait forward.

Now with Carrara, if I render using G-Buffers (alfa channels), it gives me some pretty confusing output. I am sure if I use "Channel Calculations" in Photoshop, I could probably use this output to achieve my purpose. I guess my question is. Where can I find a tutorial or does anyone have some insight as to how to use these strange alpha channels?