Vision mixer
Vision mixers were regular members of the production crew of the 1963 version of Doctor Who.
During the recording of a programme, they sat in the control booth above the studio floor and decided when to switch between the — usually four – cameras that were being used to film an episode, according to the director's instructions. They were thus "live editors", who controlled when a particular camera was actively recording.
They also were responsible for some visual effects, such as the insertion of pre-recorded material played back into a scene, and indeed the achievement of the original title sequence. Undoubtedly, however, their most important visual effect was that of regeneration, which — as established by Tenth Planet vision mixer, Shirley Coward — was always achieved by some form of camera cross-fade.
Interviewed on The Sensorites DVD extra Vision On, early Harnell-era vision mixer, Clive Doig, had this to say about his job:
What I'm doing as a vision mixer is cutting to the camera against the dialogue of the [camera script that the director has prepared]."
Because no mainstream DWU show after Survival has been produced in a multi-camera environment, vision mixers essentially haven't been used since 1989. Very brief exceptions occasionally crop up, however, as when characters are seen to be watching television programmes. The clearest examples of vision mixing in the BBC Wales era are perhaps Trisha Goddard's scenes in Army of Ghosts.
Although Survival was the final story of the regular run of Doctor Who to employ a vision mixer throughout its production, the last BBC-licensed story to use vision mixing was The Curse of Fatal Death. It in fact parodied the work of vision mixers in the original series by showing how quick cutting between cameras created the "endless corridors" down which the Doctor and his companion typically ran.
