I knowthis question isn't very specific but here goes. I'm looking for advice on how to key out sky behind some mature trees. So far I've used a luminance key but it always seems to either leave me with an annoying glow around branches or keys out some some bright areas on the tee trunk. This shows up when I drop a 3d element behind the keyed image. I have a duplicate of the original image behind the 3d elements to put the sky back in where it is needed. The trees are middle distance.