Re:Bouncing DVD Logo
by TylerE on Thursday April 16, 2020 @02:06AM
(#22886600)
AC power is 60hz so room lighting (especially florescent) also flickers at 60hz. It’s a sort of wagon wheel effect.
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I dropped a hint right there that the AC frequency is definitely not 60 Hz where I am.
Actually you didn't. There were many countries that used PAL for TV broadcasts but have 60hz AC.
They didn't say PAL, they said "50 Hz TV."
PAL and 50 Hz TV are not synonymous. Brazil has 60 Hz AC and uses PAL-M which is 60 Hz TV. AC=TV even in these odd cases.
Old CRTs couldn't possibly clock their flyback to anything but mains.
Hmm, afaik the framerates were chosen to be equal to the AC freq so that there are no glitches in the image. Do those countries have converters or something in the TVs, or did they watch jumpy image?
Fluorescent lighting, assuming it's not starting to fail, flickers at 120 Hz because each half cycle lights it up equally (+ or - doesn't matter). Incandescent also has 120 Hz flicker but the valleys are almost as bright as the peaks (slow response) so it's essentially imperceptible.
Cheap LEDs like some holiday minilights are rectified so they'll flicker at 60 Hz and I can't stand them.