I am used doing composting in After Effects but for this project I am using the Keylight plugin in Final Cut Pro. I could swear there was a way to create a mask and have only what is inside that mask be effected by my filter settings, so i don't get transparency for the spill of my green screen, but I can't for the life of me figure out how to do it in this program. I suppose if there is no other way to do it I can simply place the original image behind my adjusted image with the shot I am composting in in between the two but that seems so redundant, can anyone help me?
Honestly I think it would be better to do the keying in a different program - especially if you want to use a mask. I actually didn't even know keylight worked inside FCP. But i've had a lot of luck with it in AE. Just make sure to render out color + Alpha. Just my thoughts. Hope that helps.