A little more evidence

In a recent post, I was talking about why televisions refresh their picture at the same rate as the mains frequency. As far back as 1939, I said, flicker caused by the mains-driven studio lights beating against the picture-taking frequency of the studio cameras was being cited as a reason. Supporting (if anecdotal) evidence comes from "An unreliable and wholly unofficial history of BBC Television Centre", by Martin Kempton, which recounts how studios TC6, 7 & 8 were equipped in the 1960s with kit to allow them to create programmes in the American NTSC standard. This involved running the cameras (and other equipment) at a field rate of 59.94Hz, whereas the studio lights were still driven at the UK mains frequency of 50Hz. Martin reports that flicker caused by beating of this kind was indeed a problem when the studios were operated in "NTSC mode". It seems that few NTSC programmes were made at TVC, in part because of operational issues such as this one, but also because high-quality "standards converters" for turning PAL programmes into NTSC ones were entering operational use at around the same time as these studios were commissioned (including the "field-store" converter developed here at Research Department).

As we investigate the effects of higher frame rates on video quality, this is something we will have to bear in mind...
  • Posted: 06/07/07 01:21PM
  • Category: BBC

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