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  • Eric Leung1 Level 1 Level 1 (5 points)

    Hi Dovez, for what I have tried, setting the screen to full brightness doesn't do much help.

    Using softwares like flux together with full brightness may seem to help a little bit, but eyes would still tired out soon after.


    By they way, may I know if your eyes feel similar to us when looking at the LED screens?

  • Dovez Level 1 Level 1 (0 points)

    CCFL or LED has made little difference to me so far. I used to get eye pain from both. Now I mainly have headaches. On some LCDs I can avoid headaches completely if I set the brightness to maximum, on others I only get much less headaches with full brightness. My main problem with LCDs is definitively PWM, when the duty cycle is better I get less or none problems. I wonder what else could be causing identical symptoms of PWM flicker in others with PWM-less LCDs. These symptoms are either flicker symptoms or eye strain symptoms. The flicker symptoms would be backlight related, but the eye strain ones would be screen related. So far I have read about Ipad 1 causing Stefan no symptoms and Ipad 2 with the exact screen properties as Ipad 1 causing him symptoms. This leads me to believe that it isn't the screen. But with no PWM and reducing blue not helping leaves no parameters of the backlight to be blamed, unless the theory of MauiTechnoGeek2 is true and some undetectable flicker is present. Perhaps some LEDs behind the LCD are constantly lit and others use PWM and the light gets mixed so it doesn't show on the tests. The question of how they are dimming LEDs without color shift without PWM is extremely interesting to me. If they used some other way than PWM, then the devices with LCD screens would have to become much more expensive, which I think isn't true for the new models. Are they much more expensive than the older models with PWM? I still don't know whether it's the screen that's bad for others or the backlight. The test with the wall reflecting the LCDs light would clarify this.

  • StefanD13 Level 1 Level 1 (0 points)

    Yes setting the brightness to 100% does help me a lot, actually at work is the only way I can work. Luckily the office is bright and the display is older model (not so bright) so I don't need to wear sunglasses :).

    Also using the D-SUB input reduces the brightness compared to DVI.


    I tried using the ipad 2 with 100% brightness and wearing sunglasses but is uncomfortable and cannot say if it really helped, I didn't wait so long in order for the discomfort to transform into headache (coward). I want to believe that I'll find a more elegant solution than wearing sunglasses...


    My current opinion is that Maui is right and there is always PWM although not always measureable due to a smart controlling and that PWM is the main cause here, although I have feeling using f.lux brings an improvement as well.

    Apparently there are PWM controlling schemes which are much better than others (ipad 1, iphone 3gs, 4), but probably more energy consuming. One flaw of this theory is thiugh then why stand alone displays are not implementing this "better" PWM, so far all measured stand alone displays ( are using the classic PWM with a frequecy around 200, 300 Hz.


    And a short paranthesis to LED lamps, at least the ones I tried were heavily flickering at exactly 100Hz, seems half of the LEDs are hard wired to each AC phase. However the lamps I bought were very cheap. Incandescent bulbs also flicker at 100Hz, but with a softer curve. The CCFL bulbs seems best, there is only a very very slight oscillation at 100Hz (however I heard was not so some years ago and there were even lawsuits around this issue which finally led to improvements in the technology)

  • Eric Leung1 Level 1 Level 1 (5 points)

    Dovez wrote:


    Perhaps some LEDs behind the LCD are constantly lit and others use PWM and the light gets mixed so it doesn't show on the tests.


    This is very interesting idea!


    Despite our uncomfortable feelings matches very well with flickering light, I was starting to give up on that assumption since none of our tests shows PWM in the recent Apple displays.

    Your idea gives another possible reason why we can't detect PWM using the "simple camera waving method"! (the other possible reason is that the PWM is at very high frequency PWM)



    Speaking of fluorescent light. I found that some are more comfortable than others. Among the CCFL displays I have tried recently, I feel that the Apple aluminum cinema displays are more easy to the eyes comparitively.

    And then for general lighting, the more widely used T8 tubes seems to be more comfortable than the newer and more energy efficient T5 tubes.


    In my search on whether the blue light is the main cause of my eyes discomfort, I have ordered a pair of glasses with rose red coating named FL-41 recently. This coating blocks some of the blue and green lights and is said to be particularly effective in helping people who are sensitive to flickering fluorescent lights. (many of them have similar symptoms to us looking at LED).


    While I'm not particularly sensitive to fluorescent lights, putting on that FL-41 coated glasses does seem to give me some sense of relief when I'm inside areas with bright fluorescent lights! And seems to have a little positive feelings when I'm looking at the CCFL screen too.


    Since you mentioned you have issues with fluorescent backlit displays as well, perhaps you can give these glasses a try and see if that helps.


    And for others who wants to know if this pair of glasses can do any help to the LED screens. As much as I have hoped, I'm sad to say that I felt almost no benefit wearing it when using my MacBook Air...... 

  • CoreLinker Level 1 Level 1 (0 points)

    Here is a list of LCD displays, other than Apple, which don't use PWM at all and have a constant backlight:


    Dell U2713HM

    HP ZR2740W

    Samsung S27B970D

    DGM IPS-2701WPH


    They are all high-end 27" LED-backlit displays. I think the HP is the cheapest but has criminally poor features (basically you can control backlight intensity, that's it). Someone here said it was a big improvement over Apple something comfort-wise.

  • Dovez Level 1 Level 1 (0 points)

    Eric, perhaps the reason for your symptoms are EMFs. I wouldn't recommend listening to the experiment that I'm about to suggest, but I will suggest it anyway. Try not looking at the display but to keep your problematic device close to your head for as long as it takes for the symptoms to normally appear. If you're fine, then it's not EMFs.

  • FNP7 Level 1 Level 1 (0 points)

    I've always thought that PWM sounded like a plausible explanation for the eyestrain, but I'm having second thoughts now, because I just bought the Samsung Galaxy Tab 7.7 with Super AMOLED Plus, and found that it causes me exactly the same, significant, eyestrain as I get from LCD/LED displays (Apple and otherwise). I returned it immediately.


    I'd always understood that OLED tech doesn't use backlights or Pulse Width Modulation at all, so now I'm really baffled by this. What's even more confusing is that, while I can't use the Tab 7.7, I get no problems at all from using my Samsung Galaxy Note (1st gen) – HD Super AMOLED. 


    I’ve tried looking into the difference between those two displays (which seems to come down to the different pixel matrix they each use), but I can’t find anything that readily suggest a rationale for my different reaction to them both, or that might uniquely link the Tab's display to the tech of LCD/ LEDs (they're both RGB - RGB matrix, but so too are most CRTs and CCFLs, from what I can see).


    All very confusing...

  • Dovez Level 1 Level 1 (0 points)

    Amoled technology uses PWM. I saw the flicker of my Amoled phone when I looked thru my computer's rotating fan.

  • Dovez Level 1 Level 1 (0 points)

    Eric, could you plese try if putting a completely white pictute into fullscreen mode and looking at it in your problematic device with no PWM causes you more symptoms than putting a black picture into fullscreen mode. If so, then we only have 2 suspects: pixelation of the screen, backlight,   for the pixels are like they're turned off when they are white. If looking at the black picture causes you more or the same discomfort, then we have two suspects to blame: something with the screen and EMFs. Perhaps you could try black fullscreen first, for it is more likely to cause no symptoms. You too could try the same, Stefan. I'm really interested in the results. Btw, I tried Iphone 4 for 30 minutes and seemed to have no headaches with it.

  • willison Level 1 Level 1 (0 points)

    I need a little bit of advice. I need a monitor asap for school purposes - I'm thinking 27" so that I can sit far from it and blow the text up big. I have eyestrain 24/7 which started while I was using a CCFL, but I really have no idea if it was caused by that monitor since I tolerated CCFLs for years. Basically, I pushed my eyes too far. I was bursting blood vessels in my eyes, the pressure was so bad. Since I cannot look at any monitor at close distance without pain, it is hard for me to determine if the problem is related to LEDs but I absolutely do not want to add a new problem. I am looking for a new moniotor, one that is easiest on the eyes. I have read much of this discussion, although eyestrain is actually a large barrier for me. Should I go for the one of the PWM-free LEDs? Or perhaps one of the CCFLs from NEC? I checked out the new MBPs with retina at the Apple Store and I found it very easy to look at. Conversely, the IMac was noticeably uncomfortable from the start.


    I have a couple of contributions to make.


    1. Have any of you tried the yellow tinted eyeglasses from Gunner? These helped me for a while, but I often felt a tad bit nauseous while wearing them.


    2. The two factors that cause eyestrain are accommodation and convergence. Accommodation is the process of bringing objects in near vision into focus. Convergence is the process of converging the eyes at a single point. In both cases the muscles that do this work must work much harder at close distances. The closer you are to the object you are trying to keep into focus, the harder they must work. In the case of accommodation, the muscles that must do this work are called the cilliary muscles. Sometimes they can build up too much tension or go into spasm causing eyestrain or pain. Sometimes this is called accommodative spasm or cilliary spasm. Tension in these muscles often makes individuals temporarily myopic after long periods of close vision work. This is one of the reasons that you are given drops to relax the cilliary muscles and dilate your pupils before an eye exam.


    The other candidate for eyestrain is tension or trigger points in the orbicularis oculi muscle surrounding the eye. This muscle is responsible for blinking and squinting. You can massage some of the trigger points in this muscle with your finger tips. Search for tender spots on your eyebrow and in between your eyebrow and your eyeball. Do not massage your eyeball.


    I wonder if something about LED backlit displays is causing muscles in and around the eye to tense more than they normally would or if the problem is more related to how your brain processes the light.


    3. Computer monitors can make dry eyes much worse. Especially in the early stages of dry eye disease one may only experience symptoms while using a computer monitor. It could be mistaken for eyestrain and dry eyes can cause eyestrain and headaches. Next time go to your optometrist have them try and express your Meibomian Glands, which are tiny oil producing glands on your eyelids that keep your tears from evaporating too quickly. Lubricant eyedrops are not really objective test for dry eye disease, since they provide relief for only 30 - 60 seconds in some cases.



  • Dovez Level 1 Level 1 (0 points)

    I would go for one of the LCDs that Corelinker mentioned above. PWM-less makes all the difference for me and maybe it will for you.

  • StefanD13 Level 1 Level 1 (0 points)

    Yesterday my computer at work was updated from XP to Win7. And guess what, same issues as on the MacBook appeared. The notebook (Lenovo) was and is used only at 100% brightness so it is not a PWM issue.

    Now I can use it only with external monitor over the VGA input (as I do at home) - and is still a bit worse than the iPad 1 which gives me absolutely no eye strain...

    Using DVI is same bad as using the notebook own display.

    All this seems in line with other experiences reported here where AMOLED display causes eye strain, or same monitor used with 2 different computers behaves differently...


    By the way, disabling font subpixel rendering (clear type) didn't help (you'll find this alleged solution if you google for win7 eye strain)

  • Dovez Level 1 Level 1 (0 points)

    I can only think of more EMFs being produced by Windows 7, whith Win 7 putting more load on the computer, espacially the processor. I guess it's not it if an external monitor helps. Does it really help much? I got that it does, so the problem seems to be in the screen. What could win7 be doin with the screen that's different than in wiXP? We seem to be narrowing down the problem.

  • Dovez Level 1 Level 1 (0 points)

    If I were you, Stefan, I'd try the Lenove with windows 7 with an unnative screen resolution. This might solve it (or not). Give it a try!

  • StefanD13 Level 1 Level 1 (0 points)

    Strange that you ask, I had indeed feeling it is better, although not tried for longer period.

    Same with the macbook when I had it connected to the AppleTV->causing non-native resolution on the notebook display...

    Do you have some theory based on this? Personally I think EMF it's a dead end.

    Somebody else here said something about RAMDAC, this would match with the improvement when using the VGA input.

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