Define chroma keying and name two common colors used as backgrounds.

• A. A technique to track motion in 3D; colors cyan and magenta.
• B. Keying technique to remove a colored background; common colors: green and blue.
• C. A method for adjusting exposure; colors white and black.
• D. A process for stabilizing footage; colors yellow and orange.

Answer: (B)

Chroma keying is the process of removing a specific color from a video so you can replace that background with a different image or scene behind the subject. It hinges on isolating that color across the footage and making it transparent for replacement. The two most common backgrounds are green and blue screens. Green is favored because cameras capture its channel strongly, and it’s easy to light evenly across a large surface, yielding a clean key with less noise. Blue is used when green would clash with wardrobe or props or if you need an alternative due to spill issues, and it keys well too, though lighting must be careful to avoid noise. This technique isn’t about tracking motion, adjusting exposure, or stabilizing footage.