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Old March 18th 17, 01:58 PM posted to uk.tech.digital-tv
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Default TV system conversion

"Bill Wright" wrote in message
news
At the time when when I was a baby the only way was to point a camera at a
screen. Results were unimpressive.


I remember in the 1970s on News at Ten, you'd occasionally get footage of
breaking news stories in NTSC-land (eg USA, Japan, Africa or South America)
which had the tell-tale rapid 5 Hz flicker and geometric distortion which
showed the the UK news crew had taken (with or without permission!) local
footage and re-photographed the screen with their film or video camera -
presumably because there wasn't time to get a standard-conversion done. Not
pretty, as you say.

What always used to intrigue me was that you could always spot local TV news
footage from France or Russia, even though no line or frame rate conversion
is necessary between SECAM and PAL. As far as I know, French and Russian
equipment records in PAL and only converts to SECAM for transmission (for
ease of mixing captions on top of footage, and to use more widely-available
rather than niche-market equipment), so you'd think that UK news teams would
be able to get a clean copy without any SECAM-to-PAL artefacts like speckle
and streaks on the edges of saturated colours.

Does SECAM use the same gamma and black level as PAL, or do you get the same
problems as with NTSC where their pictures look very artificial and
plasticky. Mind you, even on NTSC tellies, US pictures look odd, in a way
that is difficult to define - something to do with contrast and tonal range.
Admittedly it was on a multi-standard TV (NTSC/PAL/SECAM) that my sister
bought in the UK for when they lived in the US for a while, so maybe the
NTSC signal was being decoded using the PAL gamma constant, though you'd
think a true multi-standard TV would cater for differences like that.