Chroma key compositing, or chroma keying, is a visual-effects and post-production technique for compositing (layering) two or more images or video streams together based on colour hues. The technique has been used in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture, and video game industries. A colour range in the foreground footage is made transparent, allowing separately filmed background footage or a static image to be inserted into the scene. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as colour keying, colour-separation overlay, or by various terms for specific colour-related variants such as green screen or blue screen; chroma keying can be done with backgrounds of any colour that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from any human skin colour. No part of the subject being filmed or photographed may duplicate the colour used as the backing, or the part may be erroneously identified as part of the backing.
Film set for The Spiderwick Chronicles, where a visual effects scene using bluescreen chroma key is in preparation
Demonstration of the creation of visual effects techniques using chroma key
A live broadcast of Myx TV using green-screen chroma key. Note the lack of shadows on the screen. The whiter area near the center of the image is due to the angle this photo was taken from, and would not appear from the video camera's angle.
Image: Girl in front of a green background
Visual effects is the process by which imagery is created or manipulated outside the context of
a live-action shot in filmmaking and video production.
The integration of live-action footage and other live-action footage or CGI elements to create realistic imagery is called VFX.
The Man with the Rubber Head
A period drama set in Vienna uses a green screen as a backdrop, to allow a background to be added during post-production.
Composite of photos of one place, made more than a century apart