Previous 1 30 31 32 33 34 Next 2,377 Replies Latest reply: Apr 13, 2016 2:01 PM by Gurm42 Go to original post Branched to a new discussion.
  • CoreLinker Level 1 Level 1

    mvanier, that video doesn't tell us anything new, it just shows a LED monitor that happens to flicker and a CCFL monitor that happens not to. Both types come in both varieties, flickering and flicker-free. Newer Apple displays actually do not flicker, but people here still have problems. For some flickering might not even be an issue.


    And if you're buying a CCFL monitor you should be looking at NEC. People here have only positive experiences.

  • mvanier Level 1 Level 1

    I'm sure the NEC CCFL monitors are fine too.  An interesting side-note is that Dell specifically chose to use CCFL backlights in recent high-end monitors to get better color range, so CCFL is not dead technology yet.


    As for the statement "newer Apple displays do not flicker", I've seen no convincing evidence to that effect (please enlighten me if I've missed something).  Apple doesn't release its backlight specs as far as I know, so until someone points a 600 fps camera at a newer Apple monitor I will reserve judgement.  If you don't use PWM you have to lower current to dim an LED backlight, and that will change the color temperature, possibly messing up color accuracy.  I could see this being acceptable on an iPhone perhaps, but not on other Apple monitors.  I still have no explanation as to why the iPhone screen doesn't bother me while larger LED screens all do.


    Now, what Apple monitors may be doing is running PWM at a higher frequency than other monitors do.  However, my visual inspections show that Apple monitors are as bad or worse at perceived discomfort than other monitors I've seen, so if they are it isn't helping.


    And yes, CCFL monitors do flicker, but the flicker is much less irritating in my experience.

  • CoreLinker Level 1 Level 1

    I've seen a LED TV that flickered at a rate of 1200 times per second, and it's flicker was just as easily distinguishable (by a simple hand wave, actually) as displays which flicker at a much lower rate. I would say pretty positively that newer Apple devices simply do not flicker.

  • mvanier Level 1 Level 1

    Interesting... do you remember the make of that LED TV?

  • StefanD13 Level 1 Level 1

    I would bet in the video the ccfl is at 100% brightness.

    I have a 1000 fps camera and indeed cannot see any flicker on some of the latest Apple products (MacBook Pro 13 and both Airs and iPad). I'm quite sure though all Apple products are now flicker free.

    Still my problems are there and thinking that 1000fps is still not enough, repeated the tests with an oscilloscope with same result - no flicker

  • mvanier Level 1 Level 1

    Very interesting.  This begs the question: how do they do the dimming if not through PWM?  My understanding is that reducing the current would shift the color temp of the backlight to an unacceptable degree.

  • MauiTechnoGeek2 Level 1 Level 1

    Here's pure conjecture.  I learned about LED display construction from here:

    The LEDs are arranged in a row along the top or bottom of the display, and optical layers spread the light out evenly over the screen.  If there are enough LEDs, then pulse width modulation can be dithered in its phase without causing much spatial variation in time on the screen.  There is a tradeoff between how many increments of brightness one can get and how uniform the light over the screen can be.  To get 8 increments of brightness, you would knock out n out of 8 LEDs at any one time, as evenly spaced as possible over the LEDs, shifting which LEDs are out.  As long as the optical system can blend together a width of 8 LEDs, no pulse will be detected on the screen.  However, if their light is not totally blended, one may be able to detect pulse on small spatial scales.  So StefanD13, you might try focusing your probe on a very small section of screen, very close to top or bottom edges, and see if you can detect any flicker.

  • MauiTechnoGeek2 Level 1 Level 1

    Under this hypothesis about how PWM is dithered among the LED lights, the greatest spatial variation–and thus most detectable flicker–would be at brightness just one notch below max, or one notch above black.

  • mvanier Level 1 Level 1

    Interesting idea.  One possible problem is that if there are too few LEDs and low brightness, then motion artifacts could be produced.  For instance, if you divide the LEDs into 8 groups, and go from +------- to -+------ to --+----- etc., you might see a line of brightness moving along the screen, which might account for the motion sickness some people have reported, as well as eyestrain as the eyes subconsciously track the movement.  You might get clever and move the lighted part around randomly or quasi-randomly to defeat this, at the cost of considerably more complex circuitry.


    BTW I've been using the f.lux program on my old CCFL monitor and I was very surprised how much of a positive difference it made even on a monitor I don't have problems with.  As others have pointed out, there are at least two distinct phenomena at work here: flicker and blue light sensitivity (though they may be synergistic where eyestrain is concerned).  CCFLs produce lots of blue light, but still quite a bit less proportionally than white LEDs (no massive spike in the blue part of the spectrum).  I'm not sure if anyone has posted this link before, but it's worth reading:



    It's quite alarmist, but there is a lot of interesting information there too.  I was not aware of the problems of focussing blue-lit objects.  Maybe this is why traffic lights are red, yellow, and green only.

  • djucsb Level 1 Level 1

    Has anybody tried inverting the colors through system preferences > accesibility? It seems to be helping me. I couldn't figure out what was going on for the longest time until I found this thread. I've had brain MRIs done with doctors thinking something is wrong with my brain because of the severe headaches and motion sickness I've had. I knew it was from this screen. I get a sharp headache around my left eye and motion sickness every time I start using my 2010 macbook pro. I tried inverting the colors and it seems to help.  I feel like a white background is the worst when trying to read text.

  • mvanier Level 1 Level 1

    What a cool idea!  I agree that white backgrounds are awful for long-term computer use.  I have a bunch of tricks I use to change backgrounds to either dark or a dull gray, which is much easier to deal with.  Firefox is a much friendlier browser than Safari in this respect, since there are several add-ons that let you change background colors.  When I use a terminal (which I do a lot, being a programmer) I usually set it to a dark green background with light gray text.  But I would still recommend you invest in an external monitor, preferably a CCFL one.


    On another topic, has anyone ever used the HP Dreamcolor monitor (the LP2480zx)?  It's insanely expensive (list price $3500, available for under $2200) but uses RGB LEDs in a backplane as the backlight.  You can adjust the backlight color temperature to whatever you want.  As far as I know, this is the only monitor out there that uses RGB LEDs for the backlight, and is targeted at industry professionals who absolutely must have perfect colors (edge-lit white LEDs don't come close).  Here's a video (basically just an extended ad, but it does show what the monitor can do):



    What I want to know is if this monitor causes the same problems as other LED monitors in sensitive people like us.  You could theoretically dial down the blueness of the backlight as far as you want, so blue light shouldn't be a problem.  Flicker could of course still be a problem.

  • StefanD13 Level 1 Level 1

    I don't know if RGB LED but HP ZR2740w was tested by (sorry only german) to be pwm free.



    My assumption is that it is RGB LED, also users with same issues as ours, report in the forum about positive experience with the monitor (no eye strain).


    And a side question... Does anyone knows how AMOLEDs are dimmed? To my understanding each pixel is controlled separately, including brightness.

  • stanillee Level 1 Level 1

    Bad news for me.


    This weekend I went to my local apple store and had my iPhone 4s swapped over due to call quality.

    Lovely new phone. Immediate eyestrain and nausea!


    The one device left that didn't give make me feel like death seems to have crossed over to the dark side.

    Don't know if anyone else has had issue with the iPhone. Having had a multitude of iPhones I had come to the cOnclusion that this would be safe.


    My request again. Begging. Does anyone know of any up to date laptops that do not cause these symptoms? I tried the new MBP retina display for a day and it was almost fine. Eyes were tense but no headache or nausea. But too expensive to keep.


    Any suggestions would be very gratefully recieved.



  • mvanier Level 1 Level 1

    Suggestion: get an external CCFL monitor for your computer.  There may be some older laptops that have CCFL monitors but nearly all new ones use edge-lit white LEDs, some worse than others.  I hope that OLED displays, when they reach laptops at a reasonable price, will be better.

  • ds store Level 7 Level 7

    Does anyone have this sort of problem on the anti-glare models?



    Hit "reply" to my post and use the quote " so I can see it as my eyes are bad from glossy screens (pre-LCD matte CRT buggers)

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