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Comment by bluGill | Hacker News Reader

Have you ever seen something running at 30 Hz? Or even 15? The difference in flicker between 30 and 60 is much much larger than the difference between 60 and 120! Yeah 60 isn't flicker free, any finite number is not (there is probably quantum limits), but realistically you reach a point where you can't really tell. For most purposes 60Hz is close enough, though you can still tell.

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I don't remember frankly. For what it's worth, TV sets would always be 50 Hz here (PAL) (unless they did some tomfoolery I'm not aware of and ran at 100 Hz "in secret" or something) and evidently I could watch those on end without too many holdups for years and years, so clearly it wasn't a dealbreaker. But on monitors, yeah, I just wouldn't tolerate it, whereas 85 Hz felt perfect (no discernible flicker for me that I'd recall).

- I hear that some later digital PAL TVs stored an image in a framebuffer and scanned it out twice at 100 Hz, which retro gamers today avoid because it increases latency relative to direct scanout.

- I've heard mixed reports over whether CRT monitors had faster-decaying phosphors than televisions. Maybe part of it is a computer has a white image, which causes more noticeable flicker than a dark background with white text (or darker TV scenes).

My old amber and green CRTs definitely had slower phosphor than any TV. They couldn't show a normal TV frame rate without huge ghosting. They also didn't have noticeable flicker though even in black on white mode (some programs could do that and my monitors also had an inverse video button)

I took film photos of my family's color TV in the 90s with a fast shutter speed. About 20% of the screen was fading at any given time with the (NTSC) 60Hz field rate, the rest being black, so to get a screen that was physically flicker-free with those phosphors, you'd have to refresh it at somewhere around 500Hz. I doubt color CRT monitors had faster-decaying phosphors than my color TV.

I looked up my brightness measurements of a Gateway VX720 VGA monitor (like Diamond Pro 710), and it seems the blue and green phosphors decay to 50% brightness in under 30 microseconds while red stays bright for 300 microseconds. I didn't measure how long it took for them to go to near-black levels. Sadly I never took measurements of my Trinitron TV when I still had it. All in all the results are inconclusive.

That sounds a bit faster than what I remember from my photos of the TV.

That's interesting. 60hz TVs always gave me headaches but my 75 hz computer monitor didn't.

I think it was actually the interlacing and not the refresh rate that did it.

> TV sets would always be 50 Hz here (PAL)

but only half the screen at a time so in effect every other line was flickering at 25Hz

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