A process used to blend together two or more images. Best known for weather broadcasts, blue screening works by placing an actor or image in front of a blue screen, applying a mask to identify the picture's blue elements, and replacing them with another image, known as background. Blue was originally chosen because it best contrasts with skin color, but green and red are used also. The process is now used for creating composite computer images using software such as Ultimatte (www.ultimatte.com) by Ultimatte Corporation of Chatsworth, California.
