does the 9.7" iPad Pro have a "ficker-free" backlight?

Discussion in 'iPad' started by bryanrs, Nov 25, 2016.

  1. bryanrs macrumors newbie

    Joined:
    Jul 4, 2016
    #1
    I was thinking about getting the 9.7" iPad Pro and I was wondering if anyone knows if it has a flicker-free backlight (I believe this means a backlight that does not use PWM). I plan to do a lot of reading on it, often at night, and a flicker-free backlight is a big deal for reading (it helps reduce eye strain/fatigue)
     
  2. cfs macrumors 6502a

    Joined:
    Feb 8, 2008
    #2
    If iPads are lit by an LED then there will always be flicker under maximum brightness. Here is a good article/podcast:

    "See, when your monitor is set to maximum brightness, the LEDs are glowing at full 100% strength. If you reduce the brightness setting in the menu, the LEDs need to omit less light, and this is accomplished by inserting small breaks, or pauses (flickers!) in which the LEDs turn off for a very short, nearly invisible time. When you reduce the brightness setting of your monitor even more, the breaks become longer."

    Read more https://bengreenfieldfitness.com/2016/09/what-is-the-healthiest-computer-monitor/

    I am no expert on this and only know what I read so I am sure there are others out there who know more.
     
  3. Altis macrumors 68020

    Joined:
    Sep 10, 2013
    #3
    Not all displays are PWM controlled. Some lower the brightness of the backlighting.

    Some displays even combine both, lowering the brightness until around 50% then implementing PWM to lower further.

    Having said that, I don't know what the iPad uses. I don't think it's PWM from my experience as I'm one who's rather sensitive to it and haven't noticed it when I use one.

    One thing you may want to do for reading at night is to enable Invert Colors so it's white text on black background... much easier on the eyes.
     
  4. Analog Kid macrumors 601

    Analog Kid

    Joined:
    Mar 4, 2003
    #4
    My guess would be that they do PWM it, but I don't know that for a fact. The problem is that changing the current through an LED can also change its color output-- given how hard Apple has tried to keep their TrueTone color accurate, I'm guessing they are precisely controlling the operating current.

    There's also problems with loss of efficiency and a minimum on current (thus a minimum brightness as well).

    The PWM allows them to keep it on at exactly the desired current, and then off entirely-- so the color of the output is controlled by the on current and the brightness by the ratio of on time to off time. Controlling the duty cycle finely enough also allows backlight brightness less than you'd get by running constant current at the lowest level.

    I haven't noticed any flicker, but it could be that I'm just not sensitive to such things, or it could be that Apple's PWMs are at a high enough frequency that I can't notice.
     
  5. Rok73 macrumors 65816

    Rok73

    Joined:
    Apr 21, 2015
    Location:
    Planet Earth
    #5
    Buy a Kindle for serious reading and an iPad for everything else. They cost nothing and e-Ink is the way to go if you really read a lot.
     
  6. bryanrs thread starter macrumors newbie

    Joined:
    Jul 4, 2016
    #6
    Bumping this because I think its a real possibility the new backlights are flicker free, it would make sense with the move to 120Hz display. Does anyone know?
     
  7. Jodiuh macrumors 6502

    Joined:
    Sep 15, 2009
    #7
    Notebook check should have a review hp soon. But they said no for the 2017 vanilla ipad and that drove me nuts with eye pain and headaches. No issues with air 2 or 2016 pro 9.7" here.

    PWM is the devil. It's nearly never mentioned anywhere on a product spec sheet, most folks think I'm crazy when I mention it, and it seems as tho very few sites will test for it.

    The only thing to really be done is test in the home on your own...of course ordering from a place that won't hassle you with returns helps.
     
  8. Krevnik macrumors 68040

    Krevnik

    Joined:
    Sep 8, 2003
    #8
    I don't believe either the 9.7 or 10.5 use PWM, or if they do, it is at a high enough frequency to not be a problem.

    Easy way if you have an iPhone that records 120fps slo-mo is to simply go into a store and record the screen in slo-mo. If there is PWM at any frequency of around 120Hz or lower (60Hz cycles drive me batty), it should appear in some way on the video.

    My 9.7" and 10.5" don't show any signs of PWM, and I use my iPads at fairly low brightness. Usually about 25-40%, and at 0% in dark rooms.
    --- Post Merged, Jun 21, 2017 ---
    Which is interesting, because PWM can also skew the color output. (https://www.digikey.com/en/articles/techzone/2014/feb/led-color-shift-under-pwm-dimming)
     

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