Väriavainjärjestelmä

Väriavainjärjestelmä, often translated as color keying or chroma keying, is a special effects technique used in photography and filmmaking to composite two images or video streams together. The technique involves blocking out a specific color in one layer of footage to make it transparent, allowing a second layer of footage to show through. This is commonly used to replace a solid color background, such as green or blue, with a different image or scene.

The process begins with filming the subject against a uniformly colored background, ideally a color that is not present in the subject itself to avoid accidental transparency. During post-production, specialized software analyzes the footage and identifies pixels within the designated color range. These pixels are then rendered transparent, creating a "hole" in the image. Another image or video clip is then placed behind the keyed footage, effectively replacing the original background.

Green and blue are the most common colors used for chroma keying due to their low presence in human skin tones, minimizing the risk of parts of the subject becoming transparent. The effectiveness of the technique depends on factors like the lighting of the background, the consistency of the color, and the quality of the keying software. Chroma keying is widely used in weather reports, news broadcasts, and movie production to create elaborate scenes without the need for physical sets.