Bluescreen

Bluescreen is the film technique of shooting foreground action against a blue (or sometimes green, in which case the term is greenscreen, orange or even grey) background, which is then replaced by a separately shot 'background plate' scene by either optical effects or digital compositing.

Bluescreen is typically used for weather forecasts. The presenter appears to be standing in front of a large map. In fact, there is just a blue background behind them.

Petro Vlahos[?] was awarded an Academy Award for his development of bluescreen techniques. His technique exploits the fact that most objects in real-world scenes have a colour whose blue colour component is similar in intensity to their green colour component.

The television technique of chroma keying was originally developed as an inferior imitation of bluescreen. With modern digital compositing techniques, the two techniques have converged.

The colour used in the background depends on the subject. Blue is normally used for people because human skin has very little blue colour to it. The same is also true for green, so the director can choose which colour to use depending on makeup and costume. Orange screens are often used with model photography where the model contains both blue and green components. Grey screens are beginning to be used in television for digital compositing. The grey colour is a very precise shade that a computer can pick up, allowing the subject to wear any costume or makeup.

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Bluescreen can also refer to an error message of Microsoft Windows operating systems, generally called the blue screen of death.