Is it possible to recover a colour signal from a monochrome film recording?
In short: theoretically, yes but in practice almost certainly no. To explain more fully: when a colour videotape was used as the source for monochrome film recordings (as for the majority of the Pertwee stories made available for overseas sale) the “best practice” was to use a notch filter to remove the colour signal centred on 4.43 MHz, as the film recorders used by the BBC were sensitive enough to pick out this information and record it. A recording not so treated would be liable to reproduce spurious colour on professional playback equipment, as the colour information would be detected but is present in a scrambled form (this is a similar phenomenon to that seen when multi-generational VHS copies of monochrome material are made and may play back with spurious colour on some systems). Theoretically it would be possible to recover this colour signal and descramble it to reconstruct the original colour signal. In practice this is fraught with difficulties including the fact that film r
