I have a shot in which a large hedge is in the foreground and I want to mask out and remove the background, which is mostly sky but does include some trees. Does anyone have any tips on how to efficiently do this? Using just a regular mask and then motion tracking it takes a long time and does not look real. I have tried color correcting the sky so it is a solid color and then keying it out with some success, but that still leaves the trees. Thanks!
I would suggest dealing with this as two parts - a key to remove the sky, and masks to remove the trees. Bear in mind that, since leaves are a somewhat reflective surface, you are going to hit the wall that's based on the fact that some of the leaves are reflecting the sky. You will have to do a spill suppression as part of the key, so that the sky color is removed, replaced, or at least reduced. Otherwise, the cutout is never going be believable.
I've run into this doing broadcast TV work, creating scenes for the weather system, in which the sky would be replaced into an alpha mask created around the buildings/trees, and other objects. It always worked when there were just buildings (with some color correction), but hardly ever worked when there were trees and bushes, because even when you color correct them, each individual weather system sky was a different color temperature, depending on the weather (stormy, sunny, overcast, etc.). You always had to match the foreground to the background, to a certain degree, which sort of precludes automation.
It's always best to get it right from the beginning rather than resort to fixing it in post. The fix is typically tougher to do and occasionally doesn't look as good is getting the proper shot.
Former Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA