Thursday, 6 March 2008
Episodes of Doctor Who that were originally colour but now only exist in black and white could be restored to their former glory.
In a major piece headlined Putting colour back in the Doctor's cheeks, today's Guardian reports how the colour recovery process has been made possible thanks to an error by technicians when 16mm black-and-white film recordings were made from the original colour master tapes for overseas sales before the masters were purged.
These telerecordings were liable to interference from the colour-encoded video signal, and this pattern of grey dots - called chromadots - would normally be eliminated with a filter.
However, filters were not always used, meaning the chromadots were often burnt into the film, and while at BBC Research engineer James Inselltheorised that it was possible to extract the original colour pattern and decode it.
Insell, who subsequently set up an independent group to work on the technology, points out in the article: "The quality of the film has got to be good enough to have captured this pattern. We're really talking about working from the original negatives and having an HD scan made to get as much information as possible from the film."
The piece stresses that this is not colourisation, whereby colour reference material is used or colour is invented. It quotes Insell as saying: "In the colour recovery process, what you get out are the original colours."
Such is the potential that software for large-scale colour recovery is being developed, and he adds: "BBC Worldwide is obviously quite interested in releasing archive content, notably with Doctor Who and various programmes like that."
Insell also worked on the reverse standards conversion process, which was used to great effect on various DVD releases, such as The Claws of Axos.
(With thanks to Tony Clark and Luke McCullough.)