Colour recovery (or colour restoration) is a process that restores lost colour to television programmes that were originally recorded on colour videotape but for which only black-and-white copies exist.[1] This is not the same as colourisation, a process by which colour is artificially added to source material that was always black-and-white (or for which no colour information was preserved in the black-and-white copy), or used to enhance poor-quality original sources. Colour recovery is a newer process[2] and is fundamentally different from colourisation.[2] Most of the work has been performed on PAL programmes, but the concept is not fundamentally restricted to that system.[1]
Colour recovery can be based on combining colour information from lower-quality recordings, or in the case of the BBC's new method, the particular effects created when colour source material was encoded into the common analogue television format PAL for transmission. With early colour televisions, until the mid-1980s, this could lead to a problem known as dot crawl because the encoding of colour information could interfere with the underlying signal. This causes a form of distortion in the output signal displayed on the screen. The pattern is evident even if the resulting image is recorded on film and in black and white. The colour recovery process detects these telltale patterns and uses them to decode the original colours.
As of 2018[update], colour recovery has successfully been applied to episodes of the BBC TV programmes Doctor Who (exception of the First part of the Invasion of the Dinosaurs),[2] Dad's Army,[3] Are You Being Served? and The Morecambe & Wise Show.