Blue/Green Screen Compositing

The technology of compositing blue screen and green screen has improved to the point where you can pull a Chroma key matte off of almost anything. However, the better the original photography and set-up, the better the matte extraction and composite.

Chroma key is a technique for blending two images, in which a color (or a small color range) from one image is removed (or made transparent), revealing another image behind it. This technique is also referred to as color keying, colour-separation overlay, greenscreen, and bluescreen. It is commonly used for weather forecast broadcasts, wherein the presenter appears to be standing in front of a large map, but in the studio it is actually a large blue or green background.

Concept of Blue / Green Screen
Blue Screen was originally invented as a film technique to separate the actors and composite them over another background. But why blue? Blue may have been chosen because it is least prominent in skin tone. Skin tone is made of a combination of red and green with a little blue.