7 ms·

> “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 wit

> “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!

perching_aix 1y ago
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).
- Suppafly 1y ago
  >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.
  - bluGill 1y ago
    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).
    - meatmanek 1y ago
      Wikipedia for NTSC alludes to a couple reasons why you'd want your refresh rate to be based on your power line frequency: > Matching the field refresh rate to the power source avoided intermodulation (also called beating), which produces rolling bars on the screen. Synchronization of the refresh rate to the power incidentally helped kinescope cameras record early live television broadcasts, as it was very simple to synchronize a film camera to capture one frame of video on each film frame by using the alternating current frequency to set the speed of the synchronous AC motor-drive camera. (I suspect shows that were pre-recorded and telecined for broadcast would've also been filmed at 30fps using a synchronous AC motor.) > In early TV systems, a master voltage-controlled oscillator was run at twice the horizontal line frequency, and this frequency was divided down by the number of lines used (in this case 525) to give the field frequency (60 Hz in this case). This frequency was then compared with the 60 Hz power-line frequency and any discrepancy corrected by adjusting the frequency of the master oscillator. I think later TVs would've just synchronized to the received signal. https://en.wikipedia.org/wiki/NTSC#Resolution_and_refresh_rate https://en.wikipedia.org/wiki/NTSC#Resolution_and_refresh_ra...
- bluGill 1y ago
  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.
  - perching_aix 1y ago
    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).
    - nyanpasu64 1y ago
      - 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).
      - wkat4242 1y ago
        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)
      - kragen 1y ago
        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.
- npunt 1y ago
  Monochrome CRT phosphors like P4 (zinc sulfide w silver) have longer persistence than ones used in color CRTs, so flicker is less noticeable.
- wkat4242 1y ago
  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)
- kragen 1y ago
  On a green ZnS:Cu phosphor, even 20Hz is minimal flicker.
- pezezin 1y ago
  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.
  - p_l 1y ago
    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 :)
    - pezezin 1y ago
      Our first PC was a 486 with a crappy 15" monitor, but I was too young to remember the details clearly. I can consider myself lucky, my dad was a big fan of Sony and we soon moved to a nice 17" Trinitron :)
      - p_l 1y ago
        Funnily enough, my first "personal" machine was a 486DX2, with a 15" "multimedia" monitor (meaning it had crappy speakers built-in and pretty much useless microphone). I don't really count it as "first PC" because by that time PCs have been in house for several years, but it meant I could goof off in games or Logo without asking for a turn ;)
johnb231 1y ago
MacBook Pro is 120 Hz
hollerith 1y ago
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.
- kragen 1y ago
  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.
  - hollerith 1y ago
    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.
    - kragen 1y ago
      Yeah, I'm kind of speculating here myself.

> “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!

perching_aix 1y ago

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).

Suppafly 1y ago
>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.
- bluGill 1y ago
  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).
  - meatmanek 1y ago
    Wikipedia for NTSC alludes to a couple reasons why you'd want your refresh rate to be based on your power line frequency: > Matching the field refresh rate to the power source avoided intermodulation (also called beating), which produces rolling bars on the screen. Synchronization of the refresh rate to the power incidentally helped kinescope cameras record early live television broadcasts, as it was very simple to synchronize a film camera to capture one frame of video on each film frame by using the alternating current frequency to set the speed of the synchronous AC motor-drive camera. (I suspect shows that were pre-recorded and telecined for broadcast would've also been filmed at 30fps using a synchronous AC motor.) > In early TV systems, a master voltage-controlled oscillator was run at twice the horizontal line frequency, and this frequency was divided down by the number of lines used (in this case 525) to give the field frequency (60 Hz in this case). This frequency was then compared with the 60 Hz power-line frequency and any discrepancy corrected by adjusting the frequency of the master oscillator. I think later TVs would've just synchronized to the received signal. https://en.wikipedia.org/wiki/NTSC#Resolution_and_refresh_rate https://en.wikipedia.org/wiki/NTSC#Resolution_and_refresh_ra...
bluGill 1y ago
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.
- perching_aix 1y ago
  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).
  - nyanpasu64 1y ago
    - 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).
    - wkat4242 1y ago
      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)
    - kragen 1y ago
      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.
npunt 1y ago
Monochrome CRT phosphors like P4 (zinc sulfide w silver) have longer persistence than ones used in color CRTs, so flicker is less noticeable.
wkat4242 1y ago
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)
kragen 1y ago
On a green ZnS:Cu phosphor, even 20Hz is minimal flicker.
pezezin 1y ago
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.
- p_l 1y ago
  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 :)
  - pezezin 1y ago
    Our first PC was a 486 with a crappy 15" monitor, but I was too young to remember the details clearly. I can consider myself lucky, my dad was a big fan of Sony and we soon moved to a nice 17" Trinitron :)
    - p_l 1y ago
      Funnily enough, my first "personal" machine was a 486DX2, with a 15" "multimedia" monitor (meaning it had crappy speakers built-in and pretty much useless microphone). I don't really count it as "first PC" because by that time PCs have been in house for several years, but it meant I could goof off in games or Logo without asking for a turn ;)

johnb231 1y ago

MacBook Pro is 120 Hz

hollerith 1y ago

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.

kragen 1y ago
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.
- hollerith 1y ago
  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.
  - kragen 1y ago
    Yeah, I'm kind of speculating here myself.