4 ms·

I hope future OLED displays don't have PWM flickering. Such a negative crippling an otherwise great technology.

by jtl999 10y ago

sturp 10y ago
PWM is the only sensible way to drive an LED, so you're out of luck on that score. Of course the period can be in the kilohertz range were you'll never see it.
microcolonel 10y ago
How slow do these oscillators run? It seems like that would be masked by persistence of vision prettymuch anywhere above 90Hz.
- kuschku 10y ago
  After testing with (larger, but still OLED) LEDs I've got here, it seems to be far higher. In my projects, for any frequency above 800Hz flickering wasn't observable, but still created nausea and headaches. Above 8000Hz nausea and headaches were gone.
  - cc439 10y ago
    That's interesting because I have an Oculus DK2 with an OLED panel (Galaxy Note 3 panel) and I've experienced 0 issues in what many consider the most sensitive display environment.
  - WhitneyLand 10y ago
    800Hz PWM can cause nausea? Is there any objective research supporting this? I haven't heard of anyone doing simple blind testing or controlling for other factors.
    - TeMPOraL 10y ago
      Wouldn't that make one unable to basically function in our world, given that a lot of things, even most basic LEDs, are PWM-driven, and not necessarily at very high frequencies?
      - Godel_unicode 10y ago
        I believe you're thinking of the pixel refresh rate, where 144hz is about the best you'll get and 60hz is normal, whereas PWM is used in the backlight and the frequency is indeed in the khz.
        boose_e 10y ago
        You can get at least 240hz if you're willing to pay. http://www.benq.us/product/gaminggears/xl2540 http://www.benq.us/product/gaminggears/xl2540
        dahauns 10y ago
        I'm afraid he does indeed talk about PWM. Sadly, lots of LED fixtures and displays (especially in laptops) still have atrociously low PWM frequencies...
        kuschku 10y ago
        60Hz PWM wouldn't even work in laptops – you’d have, at 60Hz refresh rate, only the following colors available: black, red, green, blue, yellow, magenta, cyan, white. As, for each frame, you could turn each pixel only either on or off. 8 colors isn’t exactly 16 million colors. To get 8-bit colors, with PWM, you need far higher refresh rates. For OLED, that’s 15.3 kHz minimum to get sRGB colors with PWM. If you only need to dim backlight, 4kHz is usually enough.
        dahauns 10y ago
        Huh? I'm talking LED backlights and lamps that regulate brightness with PWM. No color generation involved here. And these can get really ugly: https://www.notebookcheck.com/Test-Lenovo-Ideapad-310-15ISK-Notebook.173278.0.html https://www.notebookcheck.com/Test-Lenovo-Ideapad-310-15ISK-...
  - bsder 10y ago
    Please specify what you are measuring, because the frequencies you are quoting are far outside human perception limits. These also don't match the numbers being quoted by the VR guys. I'm extremely sensitive to refresh rates. I used to have two gigantic ViewSonic CRT monitors on my desk along with special Matrox video cards so that I could have high refresh rates. 60Hz gave me whacking migraines. 72Hz was fatiguing but didn't give me migraines. 80Hz+ and I was just fine. I haven't had a migraine due to refresh rates on digital displays ever. Not even for incredibly slow displays.
    - jfim 10y ago
      Keep in mind that LEDs and CRTs are two completely different things. CRTs have "phosphor decay," where a pixel hit by the electron beam will gradually turn on and fade out over time until being refreshed again. For LEDs, they're normally operated using a PWM; turn them off (0% brightness) and back on (100% brightness) fast enough and people don't really notice that instead of 50% constant brightness, they're getting 0%, 100%, 0%, 100% ... with a duty cycle of 50%. You can see that even with LCD monitors. LCD monitors with a LED backlight will have a display refresh (ie. how often the pixels can change color) of, say, 60 Hz but the LED backlight might be run at 4 to 8 KHz (ie. how often the whole backlight turns on and off to give different brightness levels).
    - kuschku 10y ago
      Remember, these are PWM frequencies, not refresh frequencies. A 60Hz LED display is usually driven by a 4 or 8kHz refresh crystal.
- wlesieutre 10y ago
  May not be visible if your phone is still, but you can see faster flickers if it moves or your eyes do. I don't have an OLED phone, but the backlight flicker on my Pebble Time is visible as I raise my arm up. Not actually a problem for watch usability, but looks funny and takes away from the image of the pebble screen as a constant object. Can't vouch for how it affects phone usage.
ClassyJacket 10y ago
I had an S6 and never noticed any flickering. Nor on my Apple Watch, which uses an LG OLED if memory serves. Is it really an issue in practice?

I hope future OLED displays don't have PWM flickering. Such a negative crippling an otherwise great technology.

by jtl999 10y ago

I hope future OLED displays don't have PWM flickering. Such a negative crippling an otherwise great technology.

sturp 10y ago

PWM is the only sensible way to drive an LED, so you're out of luck on that score. Of course the period can be in the kilohertz range were you'll never see it.

microcolonel 10y ago

How slow do these oscillators run? It seems like that would be masked by persistence of vision prettymuch anywhere above 90Hz.

kuschku 10y ago
After testing with (larger, but still OLED) LEDs I've got here, it seems to be far higher. In my projects, for any frequency above 800Hz flickering wasn't observable, but still created nausea and headaches. Above 8000Hz nausea and headaches were gone.
- cc439 10y ago
  That's interesting because I have an Oculus DK2 with an OLED panel (Galaxy Note 3 panel) and I've experienced 0 issues in what many consider the most sensitive display environment.
- WhitneyLand 10y ago
  800Hz PWM can cause nausea? Is there any objective research supporting this? I haven't heard of anyone doing simple blind testing or controlling for other factors.
  - TeMPOraL 10y ago
    Wouldn't that make one unable to basically function in our world, given that a lot of things, even most basic LEDs, are PWM-driven, and not necessarily at very high frequencies?
    - Godel_unicode 10y ago
      I believe you're thinking of the pixel refresh rate, where 144hz is about the best you'll get and 60hz is normal, whereas PWM is used in the backlight and the frequency is indeed in the khz.
      - boose_e 10y ago
        You can get at least 240hz if you're willing to pay. http://www.benq.us/product/gaminggears/xl2540 http://www.benq.us/product/gaminggears/xl2540
      - dahauns 10y ago
        I'm afraid he does indeed talk about PWM. Sadly, lots of LED fixtures and displays (especially in laptops) still have atrociously low PWM frequencies...
        kuschku 10y ago
        60Hz PWM wouldn't even work in laptops – you’d have, at 60Hz refresh rate, only the following colors available: black, red, green, blue, yellow, magenta, cyan, white. As, for each frame, you could turn each pixel only either on or off. 8 colors isn’t exactly 16 million colors. To get 8-bit colors, with PWM, you need far higher refresh rates. For OLED, that’s 15.3 kHz minimum to get sRGB colors with PWM. If you only need to dim backlight, 4kHz is usually enough.
        dahauns 10y ago
        Huh? I'm talking LED backlights and lamps that regulate brightness with PWM. No color generation involved here. And these can get really ugly: https://www.notebookcheck.com/Test-Lenovo-Ideapad-310-15ISK-Notebook.173278.0.html https://www.notebookcheck.com/Test-Lenovo-Ideapad-310-15ISK-...
- bsder 10y ago
  Please specify what you are measuring, because the frequencies you are quoting are far outside human perception limits. These also don't match the numbers being quoted by the VR guys. I'm extremely sensitive to refresh rates. I used to have two gigantic ViewSonic CRT monitors on my desk along with special Matrox video cards so that I could have high refresh rates. 60Hz gave me whacking migraines. 72Hz was fatiguing but didn't give me migraines. 80Hz+ and I was just fine. I haven't had a migraine due to refresh rates on digital displays ever. Not even for incredibly slow displays.
  - jfim 10y ago
    Keep in mind that LEDs and CRTs are two completely different things. CRTs have "phosphor decay," where a pixel hit by the electron beam will gradually turn on and fade out over time until being refreshed again. For LEDs, they're normally operated using a PWM; turn them off (0% brightness) and back on (100% brightness) fast enough and people don't really notice that instead of 50% constant brightness, they're getting 0%, 100%, 0%, 100% ... with a duty cycle of 50%. You can see that even with LCD monitors. LCD monitors with a LED backlight will have a display refresh (ie. how often the pixels can change color) of, say, 60 Hz but the LED backlight might be run at 4 to 8 KHz (ie. how often the whole backlight turns on and off to give different brightness levels).
  - kuschku 10y ago
    Remember, these are PWM frequencies, not refresh frequencies. A 60Hz LED display is usually driven by a 4 or 8kHz refresh crystal.
wlesieutre 10y ago
May not be visible if your phone is still, but you can see faster flickers if it moves or your eyes do. I don't have an OLED phone, but the backlight flicker on my Pebble Time is visible as I raise my arm up. Not actually a problem for watch usability, but looks funny and takes away from the image of the pebble screen as a constant object. Can't vouch for how it affects phone usage.

ClassyJacket 10y ago

I had an S6 and never noticed any flickering. Nor on my Apple Watch, which uses an LG OLED if memory serves. Is it really an issue in practice?