I worded that incorrectly. I have one whole scene render of 15 objects. When I bring it into a compositing program (ie A.Effects), I'd have 15 layers per frame, each containing that render of the scene with a different object's mask attached. Does the masked out area not cause extra file size, slowing down A.Effects? But…
@Aniceto & Slum: That coloured material ID pass is useful. @Cryrid: I'm not sure how to do that but I think it may be the answer to my next question. @Perma: Thanks a lot for the image. Yeah, I think I have an inbuilt thing not to read instruction sheets :) @Bbob: That's the prob I was having with the M/S/R material; as…