Friday, 7 November 2014

Production Skills - Chroma Keying (Green Screen)

Chroma keying, is a special effects technique for layering two images or videos together based on color hues (chroma range). The technique can be used to remove a background from the subject of a photo or video – particularly in newscasting and motion picture. A color range in the top layer is made transparent which reveals another image behind it.

The chroma keying technique is commonly used in post-production. This technique is also referred to as color-related names such as green screen, and blue screen – chroma keying can be done with backgrounds of any color that are uniform and distinct, however green and blue screens are more commonly used because they differ most distinctly in hue from most human skin colors.

It is used for weather forecast broadcasts, where a news presenter is standing in front of a large CGI map during live television newscasts, really it is a large blue or green background. When using a blue screen, different weather maps are added on the parts of the image where the color is blue. If the news presenter wears blue clothes, his or her clothes will also be replaced with the background video. A complementary system is used for green screens. 

Chroma keying is also used in the entertainment industry for special effects in movies and videogames. The current state of technology and available computer software, such as Adobe After Effects, Autodesk SmokeFinal Cut ProPinnacle Studio makes it possible and relatively easy for the average home computer user to create videos using the "chromakey" function with easily affordable green screen or blue screen kits and can start from around 100 pounds.


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