Chroma key. Today's practicality of green-screen compositing is demonstrated by Iman Crosson in a self-produced YouTube video.Top panel: A frame of Crosson in full-motion video as shot in his own living room.Bottom panel: Frame in the final version, in which Crosson, impersonating Barack Obama, "appears" in the White House's East Room. Chroma key compositing, or chroma keying, is a special effects / post-production technique for compositing (layering) two images or video streams together based on color hues (chroma range). The technique has been used heavily in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture and videogame industries. A color range in the top layer is made transparent, revealing another image behind. Projected Instruments. One Man Band. Future Rock Band. Desert Duel.