Quote Originally Posted by samsc
can you draw me an image of what you want?

and how you want this to work?

And the options you are thinking off?

Can you mock me up an image in photoshop and post it here?

Transparent black will turn the grey image into a transparent region - based on the luminosity of the grey.
Yep, this is exactly what I mean.
I recently created an animation of blowing leaves. The leaves are full color and so run the gamut in terms of being able to "key" one color or another. Generally speaking, I am a firm believer in using the right tool for the job. In another thread regarding color, the poster asked for greater color control and the reply was that it would take a great deal of processing power to do this on the fly. After Effects does it quite well but rarely previews in real time. I would much rather the processing power of the Mac be used at playing back all videos at full speed rather than trying to apply effects best done elsewhere.