Comment by Reason077
13 days ago
> “To minimize CRT flicker, Apple worked to achieve a vertical refresh rate of 60 Hz”
… a limitation that many Macs, and even some iPhones, are still stuck with over 40 years later!
13 days ago
> “To minimize CRT flicker, Apple worked to achieve a vertical refresh rate of 60 Hz”
… a limitation that many Macs, and even some iPhones, are still stuck with over 40 years later!
It's always surprising for me to see people regard 60 Hz CRT as "flicker-free", or "minimal flicker", etc. Whenever I saw a CRT running at 60 Hz, I'd be immediately be able to tell. Always used at minimum 75 Hz but preferably 85 Hz at home (early 2000s, Windows).
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.
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).
7 replies →
I have recently been playing with CRTs again, and something that I have noticed is that for fast-paced games running at 60 or 70 Hz* I don't notice the flicker much, but for text anything less than 85 Hz is headache inducing. Luckily the monitor I got can do 1024x768 at 100 Hz :)
* The original VGA and thus most MS-DOS games ran at 70 Hz.
I remember when I got my first computer for myself, instead of sharing with others, it was "obvious requirement" that the screen runs at least 72Hz, preferably higher. Which was why 15" CRT had to run at 800x600.
Later on, and with graphic card that had more than 2MB of RAM, I remember experimenting a lot with modelines to pull higher refresh rates and higher resolution on the 17" CRT I inherited when my father switched to a laptop :)
2 replies →
On a green ZnS:Cu phosphor, even 20Hz is minimal flicker.
Monochrome CRT phosphors like P4 (zinc sulfide w silver) have longer persistence than ones used in color CRTs, so flicker is less noticeable.
>Whenever I saw a CRT running at 60 Hz, I'd be immediately be able to tell. Always used at minimum 75 Hz but preferably 85 Hz at home (early 2000s, Windows).
Same, I remember installing some program that would let you quickly change the display settings on basically every computer I ever interacted with. It was especially bad if the crt was in a room with fluorescent lighting.
If your lighting and display have flicker at mathematical ratio you will notice unless the frequency is extremely high. 1:1 is most likely because it is easy to sync lights and the CRT to the AC line frequency which is 60Hz in the US (50Hz in Europe). 1:2 (used to be somewhat common) or 4:5 ratios would also cause issues.
Though now that I think of it, the CRT should be syncing with the signal and there is no reason that sync needs to be related to the AC line, but it does anyway (all the computers I know of generate their own sync from a crystal, I have no idea where TV stations get their sync but I doubt AC line frequency).
1 reply →
Me too. I'm also really sensitive to PWM. I tried using 85Hz on my VGA monitor but the higher signal bandwidth and cheap hardware made the video noticeably blurrier. 70 wasn't a great compromise either.
Since TFTs came I was bothered a lot less by it because the lack of flicker (though some 4 bit cheap TN LCDs still had it with some colours)
But there is less need because LCDs do not flicker (except some designed for videogames that strobe the backlight for some strange reason IIUC).
I know I found the flicker of CRTs annoying even at 60 Hz.
Strobing the backlight seems like it would allow you to not illuminate the new frame of video until the liquid crystals have finished rotating, so you only have to contend with the persistence of vision on your retina instead of additionally the persistence of the liquid crystals.
My "for some strange reason" was the wrong choice of words. I don't wish to imply that I disapprove of the reason that gaming monitors do it, just that I haven't done the work to try to understand.
1 reply →
MacBook Pro is 120 Hz