When doing sky replacements there usually shows up an unwanted edge around details. This is mostly evident when the sky is showing through some trees and branches. You do not want to shrink your matte to keep the detail there.
There is an alternative. Let’s call the sky plate S and the foreground F. Go into action with S as front and F as back. Track your S plate to the background.
Add another layer with F as front and matte. Key your F layer. Now if your edges are problematic, try changing the blend mode for your F surface to Max and then Min. One of them is going to give you a very good edge result depending on the luminance of your plates.
For other areas add another F and do a mask.
Submitter: Sinan Vural