Chroma keying is the technique of removing a specific color (usually green or blue) from footage so it can be replaced with a different background or effect. Green is most commonly used because it doesn’t closely match human skin tones, making it easier for software to isolate and remove. This lesson covers the science behind why chroma keying works, what makes a good green screen setup (even lighting, no wrinkles or shadows on the screen, sufficient distance between subject and background), and common problems like “green spill” — where green light reflects onto the subject’s edges.