Chroma Key

A video-post-production technique in which a solid, uniformly coloured background (often green or blue) is replaced with another image, video, or transparency using colour-matching software. In accessibility work, chroma key is most often encountered in the production of sign-language video content and sign-language research corpora: signers are recorded in front of a solid backdrop so that their hands and face can later be isolated for computer vision research, overlaid onto other content, or displayed as a picture-in-picture interpreter window. Blue is typically chosen when the subject has green clothing or props (and vice versa), and the backdrop must be lit evenly to avoid shadows that break the key.