A Primer On The History Of Chroma Key In Television

A Primer On The History Of Chroma Key In Television…

Was this Milton Berle chroma key sketch the first? No, but it is one of the most sophisticated early uses of the technology as it employs both chroma key and video tape editing. This was quite a feat in 1959!

Motion picture production had been using compositing for years prior to the invention of television, but it was an involved process requiring optical printers and intermediate film mattes, hardly suitable for the immediacy of live television.

In July of 1957, chroma key had its first on-air test on one of NBC Burbank’s more ambitious projects, ‘Matinee Theater’ that ran from 1955 to 1958. Every weekday afternoon, a one-hour live dramatic production was presented. The source material varied, but often it was an adaptation of some famous literary work.

A television version of the H.G. Wells classic “The Invisible Man,” lent itself perfectly for the first live use of chroma key. When the title character’s hands and head were wrapped in blue and he stood in front of a blue screen, the chroma key amplifier would replace the blue parts of the video with an image from another camera. All that would be seen in the composite shot was the man’s clothing in front of scenery being shot by the background camera, thus making him appear to be invisible.

Chroma key was developed by Frank Gaskins, NBC Burbank’s technical operations supervisor and Milt Altman, graphics arts supervisor. Together, they pooled their talent to develop what has become standard equipment on live video switchers throughout the world and now can be launched on any home computer. Today, blue has been largely replaced by the use of green, but is the same process. The key color change became necessary when video started to be compressed and primary colors began to be sampled at the ratio of 4:2:2, with luminence and green being the only fully sampled channel in most cases. -Bobby Ellerbee

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