Replace any Green Screen Background Using a Chroma Key

Without a doubt, you see chromakeys used countless times – probably every time you watch the news on TV – and perhaps you aren’t even aware of it.
Chromakeying is a process widely used throughout the television industry to merge (composite) one image (often a live one) with previously-shot footage or graphics and make it look perfectly natural.

Read the full article The ABCs of Chromakeys.