"Dave Plowman (News)" wrote:

In article ,
Geoffrey S. Mendelson wrote:
Those rates were chosen because the studio lights were arc lights and
flashed on and off at the power line rate, so the TV cameras had to be
syncronized to them or you would get moving black stripes across the
screen.

Don't arc lights work on DC?

But I don't think that's correct. For it to work, TV would have to be
mains locked. It was in the very early days, but later was pulse generator
locked with no direct reference to mains other than being nominally the
same frequency. Mains lock was really just to make receiver design simpler.

The only type of light I've seen which gives problems flicker wise on a TV
camera is fluorescent. Before high frequency ballasts became available,
the work round was to use them in groups of three - from different phases.


Early TVs often had a faint hum bar in the vertical. By being locked
to the line frequency, it was fixed to one location, and most people
never saw it.


--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.