Blue Screen(redirected from color key)
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In photography and video making, a physical blue screen against which a shot is taken. The screen enables a second shot (usually a background) to be combined with the first image. Blue screens are used in filming to make an actor look as if he/she is somewhere else. This can be less expensive than shooting on location, though blue screens are also used to superimpose very expensive CGI images into the film. A blue screen may also be a green screen.