Production Glossary
Chroma Key
Chroma key is the process by which two images are amalgamated into one polished image in the editing room. Often times, this technique is called green or blue screen, a reference to the color of the backdrops that are employed in the process. These green and blue backgrounds were originally chosen because they are the farthest colors from the natural skin tone of humans. In the process of shooting for Chroma key, it is important that the lighting is just so and that the actors being shot do not dress in outfits that have the backdrop's color in them. Otherwise, the article of clothing will be "keyed out". This technique is prevalent in movies and television. It can be used for large scale special effects, all the way down to weather maps during a news broadcast. Having the chroma key option helps TV and film producers save money on shoots that could potentially spend more time and energy than they can afford.
How It Works
A scene is being shot in which two hikers pause to look out onto a beautiful view of mountains. The director could choose to have his actors actually hike up to a lookout and shoot all the different angles of them gazing out at the beauty around them. Or, he could simply dress a set and place his actors in front of a green or blue screen and shoot the same footage. Afterwards, in editing, the green or blue image will be "keyed out", selected to have another image laid over it, such as a beautiful view of mountains, using a stock photo or video. The same effect is achieved with less time, money, and energy expended.
Check out the video below for more information configuring your own chroma key setup :
