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  • mojarvinen Level 1 (0 points)

    I think I might be on to something. I found this display testing & calibration site:



    There are a couple of interesting tests:


    Although I've set the brightness to 100 % in myh Dell 2412m and it should not flicker, I see horizontal lines moving downwards. When I adjust the Contrast, in every couple of contrast steps, the horizontal lines disappear/or stop moving.




    With the offending Dell 2412m, almost all of the screens flicker, some very clearly. I've used this test on several other displays, the displays which do not cause eye stain, and with those displays usually only 7a or 7b flicker.


    Could you test with a display that does not strain your eyes and with a display that does, whether you get similar findings. Then we could at least have a test, which could give some pointers, which displays will cause eye strain. Obviously that does not solve the problem, but maybe then a LCD display expert could point out, why the bad displays flicker and have horizontal lines and those that do not cause any problems do not.



  • Harleybros Level 1 (0 points)

    Went to Apple yesterday, showed them the flikkering of the display

    Apple is going to change the display now

    Will post the outcome when done

  • iStrain Level 1 (0 points)

    I was running inversion tests as well. I found some correlation between the test results and severity of apple motion sickness symptoms. Typically, the screens with more flickers were affecting me faster, but I have a screen that exhibits almost no flicker at all, but is still causing me motion sickness. So, at the end, my results were quite inconclusive, which is really unfortunate since it would have being such a great test to have. 


    On the positive side, our issue is finally getting some mainstream coverage. About a month ago Jake Wallis Simons posted a nice article on The Telegraph Blog damaging-our-eyes/ Needless to say, it generated a lot of comments many of which are questioning the author's credibility and professionalism.

  • Gurm42 Level 1 (0 points)

    Hey folks, anyone have an opinion on this monitor:

  hannel=Google&mr:trackingCode=32C150D5-24E1-DF11-B41F-0019B9C043EB&mr:referralID =NA&mr:adType=pla&mr:ad=22395426956&mr:keyword=&mr:match=&mr:filter=20224360076& cm_mmc=Mercent-_-Googlepla-_-Technology+Monitors_Projectors-_-634596


    I've started a new job and the Dell monitors here are terrible for me, in spite of passing most of the tests and having a minimal amount of PWM.


    I'm trying to find a monitor that will be good for my eyes without breaking the bank. These are under $200...

  • Gurm42 Level 1 (0 points)

    Essentially any recommendations would be great. My new office is a Dell shop and the monitors I have been issued are the infamous U2412Mb, really pretty intolerable. I'm sure that I can order something else, I just need to know in advance what will be pleasant since I don't want to be the new guy trying 80 different monitors until we find a good one!

  • Dovez Level 1 (0 points)

    Does it have to be a Dell? If not, I'd recommend the HP ZR2440W. It has a PWM frequency of 430 Hz, so definetly beyond the limit of subconscious perception. And if the problem is software related, just use it with a non-native screen resolution. No PWM + non-native resolution = 100% certainty of zero problems.

  • dan98 Level 1 (0 points)

    That's great info - how are you finding out the PWM frequency of a particular monitor - is this published somewhere?

  • mojarvinen Level 1 (0 points)

    I would be carefull about the HP. It still has the anti glare, which can cause problems. Also, the Dell does not flicker at 100 %, but it still causes huge problems for me. So I would suspect, that althought the HP does not flicker, it can cause problems.


    I have the Samsung S24a850 display at home, and it is a PLS panel. It does cause problems, if it is not 100% brightness, but if I set to 100% I can game/browse the net all night without problmems. It does not have anti glare coatin, but it isn't glossy. I conclude that it must be th PLS panel that helps.


    It is a bit more expensive, but I would bit the bullet, since I've used this monitor for over a year without problems, but now that I've had the Dell at work for a month, the dell causes problems, which I do not have anymore in the evening with my samsung.  Though, it is bright, but I can dim it with software, so that the actual backlight is still 100 % .

  • Topher Kessler Level 6 (9,865 points)

    MauiTechnoGeek2 wrote:


    There's a new study out:

    Chamorro, Eva, et al. "Effects Of Light Emitting Diodes Radiations On Human Retinal Pigment Epithelial Cells In Vitro." Photochemistry and Photobiology (2012).

    "Light-emitting diodes (LEDs) are the basic lighting components in screens of PCs, phones and TV sets; hence it is so important to know the implications of LED radiations on the human visual system. The aim of this study was to investigate the effect of LEDs radiations on human retinal pigment epithelial cells (HRPEpiC). ... It is shown that LED radiations decrease 75–99% cellular viability, and increase 66–89% cellular apoptosis. They also increase ROS production and DNA damage. Fluorescence intensity of apoptosis was 3.7% in nonirradiated cells and 88.8%, 86.1%, 83.9% and 65.5% in cells exposed to white, blue, green or red light, respectively."


    It's not inconceivable that LED screens could turn out to cause mass cases of eye disease after 10 to 20 years.


    This is absolute crap. It's a perfect example of how science is misused to promote some ridiculous claim. I work in the visual sciences and study retinal function, and this study is flawed. They do not provide a positive control at all, and essentially compare LED light-exposed cells to cells kept in the dark. This does not at all show a comparison between LED-exposed cells and exposure to any other light source, and also don't cover differences at different light levels.


    Here's the PDF of the article in full (its free): 237.pdf?v=1&t=ha2nvee6&s=3e1ac61eebdcf133b5dcd3d68c2ab036582c4075


    Light of any kind will result in all of those effects outlined in that paper, be it from the sun, an incandescent bulb, a CFL backlight, or an LED. An LED is just a light source with specific spectral properties. It's not shooting off gamma or alpha radiation. You can have infrared LEDs, UV LEDs, and any that cover all aspects of the visual spectrum (narrow bandpass and wideband).


    In the study they state explicitly that the light levels used are similar to staring at a 100W bulb from 20cm away for 12-hours straight. So in essence, you stare at the sun and you'll damage your eyes....well now that's something new.


    The essence of this paper only shows that under experimental conditions, the chemistry in the eye can produce toxic chemicals in response to light, and that this production has a spectral component to it (ie, it happens at a higher rate with some colors than with others). This finding is nothing new. The eye regularly produces these chemicals, but buffers them and quickly removes them to prevent accumulation.


    LED monitors are not going to hurt your eyes any more than any other monitor or light source of similar intensity will.

  • Dovez Level 1 (0 points)

    That's great info - how are you finding out the PWM frequency of a particular monitor - is this published somewhere?

  has measured some monitors for their PWM frequencies:

  • dan98 Level 1 (0 points)

    Thankyou - their reviews are incredibly thorough.

    I don't know how they are  measuring PWM but I would like to find out...that may be the answer to  side affects.

  • Harleybros Level 1 (0 points)

    He guys

    this forum is about problems with the apple display of the macbook


    suggest if you want to discuss purchasing HP monitors to go somewhere else


    would appreciate that


  • Gurm42 Level 1 (0 points)



    While I appreciate your point of view, I'd like to point out that:


    1. I've contributed a lot to this thread.

    2. I'm in some substantial discomfort.

    3. If it were easy to find threads about monitors that bug your eyes out, would so many people be here?


    Regardless, I don't think that asking for a monitor recommendation - a monitor to which I will hook up my retina MBP, by the way - is out of the scope of this discussion.


    I currently use - at home and at my previous job - HP LA2306x monitors. While they do have some obvious PWM and aren't perfect, I can use them for a lot longer than the Dells. I'd love to find one that's pain-free though, hook my MBP up to it, and get a full day's work done.


    I'd really prefer CCFL, I think? Since I just don't know what it is about current LED's that is so problematic. A PWM-free CCFL would be amazing.


    - Gurm

  • Harleybros Level 1 (0 points)

    I just came back from Apple

    they replaced the display




    no more flickering and no more headache within 10 minutes


    when you go to


    and your screen flickers, enlarge then the screen and you will see it moves up & down (vibrates)


    if so go to apple and ask them to replace your screen


    this will solve the problem !!!!!!


    Finally after one year of running to the apple store, buying 2 different pairs of glasses and having my eyes measured several times, running to the hospital (eyedoctor) 


    my problem is finally solved, it was not my eyes, it was the macbook


    what I all the time expected there was nothing wrong with my eyes, since I still could see the blond chicks, had no problems with that LOL

    yes, I can laugh again !!!

  • dan98 Level 1 (0 points)

    I just found a  PWM FREE Led .

    The Dell S2740L


    This site tests for PWM:


    Sorry to Apple forum moderators for daring to mention other brands!

    However this may be a workaround for Macbook sufferers.

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