I am using the Chroma Key technique to put my presenter in places we cannot afford to visit for my documentary. I can get this to work quite well except that I cannot get a full length shot of him presenting as if I go further back for the shots my green screen is too small and I start getting all my living room furniture(!) showing round the edges. I thought if I could crop the clip just to the area of the green screen this would solve the problem. I maybe be missing something obvious here but when I use the cropping tool I cannot see a custom crop option. Each crop seems to retain the same proportions as the original clip.
Do I have to create a mask to achieve what I want?
Regards
Nigel