Chroma key is a term used in television and motion picture production to describe the process of compositing separate visual elements into a single image. Sometimes called chroma or colour keying, the technique involves a backdrop of a solid colour, most frequently a blue screen or green screen. Walking on the moon, the Oscars, Hollywood, Special Effects, Hawaiian beach party? Chroma key allows you to take yourself digitally to any location in or out of this world.

Explanation
Chroma keying involves a subject (an actor, performer or newscaster) being filmed or photographed in front of the blue or green screen. On computer editing suites, the solid colour image is taken out and replaced with the desired image. Green screen photography can be complicated and time consuming, as you must use the right equipment and lighting. If done correctly thought the results are fantastic and very entertaining.

Blue and Green
Blue and green screens are most commonly used because they are farthest away in the colour spectrum from the colours of human skin tones.

Clothing
Subjects of a chroma key shot should not be wearing any clothing that matches the backdrop colour or that area of their body will appear to be missing.

Lighting
Lighting is very important when setting up a chroma key sequence. The subjects and the backdrop are lit separately to strive for a high lighting contrast between them.

Uses
One of the main uses for chroma-key in television that you’re no doubt familiar with is the weather report. Next time you watch a TV weather report, you’ll know that the different maps, satellite and radar images appear behind the weathercaster because of chroma-key technique.
By using chroma key technique you can show the world that you were physically present in a place where you have actually never been to.