Hasta La Motion!

I know this is a dumb question but I was wondering how you would tell if a green/blue screen is not workable.

I hear sometimes that if you are a good artist, anything can be done, but isn’t their a limit on how much you can do?

For instance, I got this really crappy shot of an actor in front of green screen. Their is poor lighting, grain, motion blur, shadows and folds on the green screen. Their is also a lot of spill on the actor, so when I use primatte or keylight, it keys a lot of the pants with it and when I adjust the parameters, I can never seem to pull a good key.

When something like that happens, what do you do? What happens in the real world when something like this happens? Do you ask for better footage or…?