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  • Jessiah1 Level 1 Level 1

    tfouto, we need someone with a spectrometer to measure the actual wavelength of light emitted by these devices to understand exactly how harmful they may be, we cannot rely on manufactures accounts for this information.


    This is an old paper from 2000 on Blue light and how it damages the retina. I imagine all of this information needs updating however there is interesting info on yellow filters and testing on animal retina's. It was written before the onset of LED lighting, imagine how it would read now if re-written....I think part of the problem with using blue light blocking filters for most of us is that these filters are supposed to prevent damage from happening not reverse the effects we are experiencing now. The real question is are these lights causing some sort of eye damage, we do not know because it is not something optometrists are trained to look for and the effects may not be obvious. Also, keep in mind not all yellow filters are blocking 100% of blue light, I imagine ski goggles are not a good example.



    I know I have unloaded tons of info today and yesterday, unfortunately there is so much more out there that everyone here could benefit from reading and this is not even a 10th of what I have read in the last 4 years.....



  • Scott98981 Level 1 Level 1

    I also found that the blue LED front light on the Kindle paperwhite is the worst thing I've ever seen. However, I try to turn the light completely off and use ambient light. Unfortunately the light does not completely turn off. However, using high-intensity ambient incandescent or florescence light or outdoor light I can read on the paper like display for many hours without eyestrain. To me this suggests that pulse width modulation and or blueshifted LED lights are sufficient to cause the eyestrain. Similarly, I still am able to use the iPad 3 and 4 or my iPhone 5 for many hours without difficulty. This suggests to me that not all LED displays produce the symptoms. I wish I knew what the difference was between the display technology of the iPad 4 and 5. I have unfortunately tried to use the iPad 5 on two occasions and had to return both times, despite this being a perfect tablet for my needs. I am aware that they started using IGZO display technology, however they apparently use significantly fewer LED backlights, which might also be using aggressive PWM to save battery life. I am hopeful that the next iPad will work for me.

  • tfouto Level 1 Level 1

    Jesse, you are right, we cannot rely on manufacters information.


    The problem with spectrometer is it really expensive. It's for professionals who use really expensive monitors. I dont think people here use those.


    I just hope that in future quantum dots technology and alike, become more widespread.

  • tfouto Level 1 Level 1

    "I can read on the paper like display for many hours without eyestrain." You can use the kindle that way?


    I guess it's better to me to buy the kindle 69$ and return the paperwhite 119$. Why pay more for the backlight i cant use. I dont understand why cant we turn off the light completly.


    The light on the kindle is really, really harsh. I suppose it's also to do with color temperature, not just spectrum.


    Real paper is the best thing to my eyes...

  • Scott98981 Level 1 Level 1

    I think either Kindle would work well. However you may be so sensitive to the LED blue frontlight that even when it is on low it may affect you. I prefer the touchscreen capability of the paperwhite. I've also used Gunnar optiks yellow lenses with the paperwhite LED with no improvement. I would imagine these lenses should filter out any offending blue light, but did not have success.


    Has anyone had success with the iPad air using reduce white point? I really want to give the iPad air another try. I need a device for reading PDFs and there are no E-INK displays that are large enough + fast enough processor to manage PDFs. So far the iPad has the best PDF rendering I've seen on any device. It's even faster than MacBooks.

  • tfouto Level 1 Level 1



    This site has reviews which shows the spectrum of light:



    Seems S5 is one the more balanced. Altough not quite at best levels...



    Compared to HTC One seems better:


  • mojarvinen Level 1 Level 1

    Would anyone have access to Galaxy S5 to test the PWM with the DSLR video test? (or the picture test)


    I have again purchased the Surface Pro 2, since there is really no alternatives - but that has a PWM frequency of something like 600 Hz and it does bother my eyes if I use it for several hours. It's not the blue spectrum, since I've tried F.Lux and also a Spyder calibration and either of those do not help.


    The PWM cannot be measured by taking a pictrue of a vertical line, but it does show up as horizontal lines if I film the screen with a shutter speed of 4000, with 25 frames per second video setting. There are clear horizontal lines flowing trough the screen, which are not visible in those displays that do not cause discomfort like: Galaxy s2 on full brightness, HPZR2740w on any brightness.


    I have without doubt confirmed that my eye irritation is exclusively due to the PWM or flicker. Flicker could of course be caused also by the much talked about dithering, but I still doubt it.


    Some say that Apple does not use PWM, but I suspect that it's not the case, the PWM is just so high frequency that it cannot be measured by typical devices, but it still irritates the eye.

  • tfouto Level 1 Level 1



    i think in your case the problem is dithering, not PWM... I have a diode that measures PWM, and if there is PWM is above 8Khz, which is really high.


    I would bet my money that you suffer from some kind of dithering, like some here...

  • mojarvinen Level 1 Level 1

    Might be. But with the displays that I have confirmed that have PWM, it is the PWM, since once the PWM component is removed, there is absolutely no eye strain. Like with the Samsung SA850. It has PWM of 240 Hz, but when the brightness is 100 % there is no PWM and no eyestrain.


    My experience with Apple products is only iPad 1 and that does seem to have PWM as per the DSLR test. Though could also be that the dithering shows up as flicker.


    But in anycase, it is the flicker for me, not blue light. I know few people like to hear this, but I'd still suggest trying onen of the displays that are confirmed flicker free. And really try it so that there is a long break after using a display that causes problems, so as to let they eyes recover. If I use the Surface Pro for several hours, it takes roughly 3 days for my eyes to fully recover.


    This is a frustrating problem, as now there are articles also in the mass media about "how to reduce eye strain with computer displays" Often these articles list PWM as one of the problems, but then suggest some incorrect things like lowering the brighness, which for most monitors just starts the PWM thus makes the problems worse.


    I was hoping the Galaxy S5 would have no PWM like S2, so I could finally get a new phone.

  • tfouto Level 1 Level 1

    Dithering is related to flicker. It's a form of flicker...


    In my case is essentially blue-light, but there seems to be here people with 2 different kinds of issues...

  • OQ3 Level 1 Level 1

    There are ways of filtering out blue light, you know? But flicker cannot be filtered out.

  • Jessiah1 Level 1 Level 1

    OQ3 "There are ways of filtering out blue light, you know? But flicker cannot be filtered out."


    Most of which do not actually filter out blue light but block a wide spectrum at a small percentage, normal sunglasses for example. Yellow filters are not blocking 100% of all blue light either, I will further this after a discussion with a PHD I will be having soon.


    "Dithering is related to flicker. It's a form of flicker...


    tfoutoIn my case is essentially blue-light, but there seems to be here people with 2 different kinds of issues..."


    Possibly, however it would be difficult to rule out either, both flicker and spectrum can exacerbate the issue in combination. In mojarvinen'ssituation it sounds like he has reasonable evidence only PWM or any form of flicker will trigger his issue however I would caution that it could still be both and here is why. His symptoms could be pre-dominantly eye strain related so blue light may contribute to the severity when flicker is present but not be the primary cause. Removing flicker may be enough for him/her (I cannot recall, my apologies) to not have symptoms however it could be due to a higher tolerance overall to blue light and flicker than others here have, it does not rule out spectrum being part of the issue with any scientific method.


    I will explain why I have this theory, myself being of the most severe group:


    I have viewed some "Flicker free" devices and played with removing PWM on CCFL/LED monitors, the result for me is continued symptoms however they are not as head pounding migraine style in the beginning as they are Vertigo and disorientation. This is on par with wavelength being the issue and when flicker is removed there is improvement, unfortunately for me the Vertigo is so bad it becomes a migraine eventually anyway. The point is removing flicker makes a difference. There are many "flicker free" LED light's out there, they are after all called "Solid state lighting" and they ALL make me seriously sick within minutes. The devices we know have LED blue light and flicker are definitely the worst and combine both Vertigo/Migraines instantly for me. In addition to this so does my pellet stove with glass window, the flickering flames which are full spectrum fire cause me to have headaches, interestingly enough it takes much longer for them to become a migraine and they are not as severe at first as Blue spectrum LED lighting. We can assume flicker is the primary culprit with the fire, correct? So there are many examples of both being an issue with different reactions when flicker or spectrum is removed.


    Hopefully I have written this out clearly? I have hoped to help others understand this very point for some time, with the severity of my situation I have unique experiences which I believe explain in theory much of the spectrum Vs. flicker conundrum!



  • OQ3 Level 1 Level 1

    Actually, I think it should be possible to block 90-100% of the blue part of the spectrum, you just need to look hard enough for such material. Everyone who blames blue light and is serious about finding the real causes needs to try it.

  • peter_watt Level 3 Level 3

    If a yellow filter does not block 100% blue light it is not a yellow filter. By definition.


    Let's be clear, blue light may exascerbate strain in certain people. It cannot damage eyes at normal levels any more than red or green, as has been claimed.


    If a poor yellow filter only blocks 80% blue light and you have problems it is unlikely to be color that is your problem. Concentrate on flicker rduction by using screens at 100% brightness and neutral filters to attenuate level. 

  • soundstar3 Level 1 Level 1

    This is the best filter i have found for the blue light. Does anyone from usa would like to try it? In europe i can't find any place who sell it at aceptable price.