Clean up keyed footage with a garbage matte

[MahaB82A]

https://helpx.adobe.com/after-effects/how-to/create-video-visual-effects.html

(4) Clean up keyed footage with a garbage matte

See this footage at time 00:40. Author says it is “very hard to see”. If it is very hard to see what is the point of repairing it?. Why do we have to bother of totally eliminating it.

[Rick Gerard · Accepted solution]

Fixing something hard to see is the mark of a professional. If I had been doing the tutorial, I would have said, "There is some noise in this area that needs to be cleaned up." Sometimes I end up with a dozen layers on a greenscreen composite to fix all of the problems that are worth fixing. Very few don't require anything other than applying Keylight.

[MahaB82A]

Thanks