Q: Eye strain from LED backlighting in MacBook Pro

And to think, I was just marveling that in this thread we hadn't had a lot of trolling or had to really light into anyone.

Topher - you are clearly confused. You claim to have read this entire archive, but that isn't possible because assertions you make contradict that claim.

For example, you claim that people haven't tried adjusting brightness. You could have, at some point in the last FORTY SEVEN PAGES, read about those of us you have tried f.lux or multiple brightness scenarios or TEN DIFFERENT SCREENS.

You also are inherently dismissive of the possibility that LED light is a source of problems for people. Even when someone comes right out and says "LED Christmas lights make me nauseous". Many in here have sensitivity to LED lights. Many people in here can't watch LED TV's. I myself can't spend a lot of time looking at the some of the LED Christmas decorations my wife has put up because they give me a headache.

My own eye doctor has seen firsthand what this does to my eyes - it makes them malfunction in a specific way that is almost as though I need reading glasses or multifocal corrective lenses when in fact I do not!

No amount of brightness adjustment, anti-glare coating, or display calibration can make a modern MBP screen usable for me. And I've got one of the milder cases in here - I have no problem with LED TV's, for example.

So get off your moral high horse. You haven't read all of these accounts, you don't experience the problem yourself, and you've already decided that everyone in here is lazy and ignorant or at best seeking validation for an imaginary problem. Guess what? You're wrong. And if you have nothing to offer beyond the - admittedly fairly well worded - platitudes you've offered thus far, we have precious little interest in anything you have to say.

Thanks.

Topher seems to be exactly one of the worst persons we can have in this kind of discussion. Now, I know that there are people who are entirely unnaffected by the problem we have, but that does not mean it's in our head.

I got my new Samsung S27B970 display on friday. It's one of the best displays that money can buy. I bought it based on the reports, that it does not have PWM Backlight control.

I tested it with lagom.nl and couple of other tests. The best monitor thus far, what comes to the tests. The image is great and with the default setting, brightness at 100 %, it is great. I almost feel like my eyes rest when I read text on it.

But then I set the baclight to 75%. Wow. Immediately I felt the discomfort in around my pupils. I tested different settings and alternated between 100 % and 0, but it was clear that there is discomfort when the backlight is not 100 %.

I took my DSLR and started making tests. The same test that TFT Central does. Made a vertical white thin line on a black background with Photoshop. Then I took pictures with a slow shutter 1/8 and high ISO, while moving the camera from left to right. And yes, the PWM flicker is obvious. When the backlight is 100%, there are no black spaces between the vertical line, it's just a even white box. When the backlight is even a bit less than 100%, there are clear black spaces between the vertical white line.

Usually, my eyes recover during the weekend, but now my eyes feel like my lids were sandpaper. Dry and swollen.

So I think I've finally confirmed where the problem is. It really is the PWM Backlight flicker.

What it isn't:

-Glossy coating

-LED light spectrum

-Brigness or contrast

What might cause additional eye strain:

-Anti-glare coating

What will cause additional eye strain:

-Flicker in the Lagom.nl or similar LCD tests.

I can use this new Samsung without problems with the backlight 100%, but it clearly is a bit too bright in the evenings and mornings, when I actually usually use it. So I'm pondering wheter I should take it back or not. Luckily I have still 10 days to return it. (In Finland you can't just return stuff if you don't like it like in the US)

So, either Samsung has changed it to have PWM backlight dimming to the production models, or the prad.de and tft central measurements were flawed. Though, the PWM flicker is not nearly as bad as with some other displays, but it's still there.

I'm considering the HP ZRW 30", which is CCFL backlit. The CCFL backlight seems to not cause problems, because, although also PWM controlled, the CCFL glows a bit after it has been turned off with the PWM cycle, so the difference is not so abrupt, like with LED's. But that display has the Anti-glare coating, so I'd just have to test that out, whether it causes problems or not.

As a conclusion I'd say that I've now found out the reason for the problem. It really is the LED backlight, when it is dimmed by flickering the LED. (And to be clear, it's not LED as such, although somone commented LED Christmas lights giving problems - maybe there is the flicker also for some reason)

Gurm42 wrote:

 

And to think, I was just marveling that in this thread we hadn't had a lot of trolling or had to really light into anyone.

 

Topher - you are clearly confused. You claim to have read this entire archive, but that isn't possible because assertions you make contradict that claim.

 

For example, you claim that people haven't tried adjusting brightness. You could have, at some point in the last FORTY SEVEN PAGES, read about those of us you have tried f.lux or multiple brightness scenarios or TEN DIFFERENT SCREENS.

 

You also are inherently dismissive of the possibility that LED light is a source of problems for people. Even when someone comes right out and says "LED Christmas lights make me nauseous". Many in here have sensitivity to LED lights. Many people in here can't watch LED TV's. I myself can't spend a lot of time looking at the some of the LED Christmas decorations my wife has put up because they give me a headache.

 

My own eye doctor has seen firsthand what this does to my eyes - it makes them malfunction in a specific way that is almost as though I need reading glasses or multifocal corrective lenses when in fact I do not!

 

No amount of brightness adjustment, anti-glare coating, or display calibration can make a modern MBP screen usable for me. And I've got one of the milder cases in here - I have no problem with LED TV's, for example.

 

So get off your moral high horse. You haven't read all of these accounts, you don't experience the problem yourself, and you've already decided that everyone in here is lazy and ignorant or at best seeking validation for an imaginary problem. Guess what? You're wrong. And if you have nothing to offer beyond the - admittedly fairly well worded - platitudes you've offered thus far, we have precious little interest in anything you have to say.

 

Thanks.

I can only suggest you stop being so defensive, and definitely cut back on the insults. I am not confused one bit, and have the right to be skeptical of some of the claims mentioned here. I also have the right to participate in this discussion, and never once said anything to warrant your ridiculous and insulting response.

This discussion is not closed to those who have differnent opinions than you, or to those who might wish to offer opinion even if it has been discussed before, so by "we have precious little interest" you perhaps only mean yourself.

Like I said, I dont discount the discomfort people are feeling even if I respectfully find some of it (but not all of it by any means) hard to believe, but do absolutely think the conclusions to blame LED spectral properties outright is far-fetched. Since there is no relevant evidence to back this up, please do not come down on me for at the very least having a different opinion than you on this matter.

Again, it's not a matter of being dismissive to the issue, but with regards to the cause I simply do not accept the claim of LED radiation as being significantly different than that from other light sources and therefore being the root of the problem (this was the topic of my initial involvement in this thread). I use LEDs all the time in my work and examine their spectral properties all the time, and some claims here about the properties (ie, that it causes damage) are ludicrous.

That is not to say that some implementations of LEDs (as with any light source) can't be bothersome to people, but the radiation of those used in screens is not harmful and their output can be adjusted so any intensities that people might be sensitive to can be put below the threshold of where it is bothersome.

Maybe you feel you have already discussed this aspect and moved on from it and therefore it should not be discussed again, but I have all the right to bring it up, and my doing so does not warrant your insults. Shame on you for being so negative, insulting, and otherwise demeaning. It's disrespectful to me, Apple, and everyone else here that you would bring such hostility into this forum.

I applaud you for working so hard to find out what exactly was the problem in your case.  You might consider some kind of external filter to dampen the brightness a bit.  A long time ago I had one of those for my CRT monitor, but I'm not sure what's available today.  Also, some monitors still flicker even at full brightness.

I think different people are sensitive to different things.  In my case, I think I'm much more sensitive to light spectrum issues than to flicker, though flicker can be annoying too.  My iPhone 4S has no detectable flicker (the display is solid as a rock) but the white light does bother me, though I've gotten used to it to some extent.  I never have this problem with CCFL-backlit monitors.  Also, using f.lux even on CCFL backlit monitors makes them significantly more comfortable for me.

My impression is that the industry has been working harder to eliminate flicker issues than spectrum issues, perhaps because they are more immediately noticeable, or perhaps they're just easier to fix.

"My impression is that the industry has been working harder to eliminate flicker issues..."

I agree, and I might argue 120 and 240 hz LCD LED tvs is evidence of that. As I've said before on this forum, the human eye can't hardly notice (in terms of perception) the difference after 60-100 frames a second, but it may be able to tell the difference (in terms of strain/pain) between a real slow flicker (eg 30-60hz) and a fast one (120-240).

mojarvinen wrote:

 

Topher seems to be exactly one of the worst persons we can have in this kind of discussion. Now, I know that there are people who are entirely unnaffected by the problem we have, but that does not mean it's in our head.

 

Now why would you say that? I've repeatedly mentioned the contrary and even explicitely said so, so why would you at all say that I'm claiming it's all in your head? I never said or even suggested that at all. Others have erroneously claimed this is what I'm saying, but I haven't said anything of the sort.

I likewise am more sensitive to monitor flickering than others I know, and while I do not have an issue with LED displays flickering, I initially only chimed in to argue against the claim that LED spectral properties are the root of the problem and are dangerous to eye health.

In looking back at my initial responses I do see I mentioned "any property" of LEDs, and I do wish to clarify that I was not thinking of temporal responses and flickering at the time. My focus when discussing this was regarding spectral responses of LEDs.

Hi all,

I was curious to see if my headache experience was possibly due to font sizes and font smoothing. So I performed a little test by VNC -ing into the MBA from my regular PC laptop. This worked fine and the screen size is about the same. So that brings me back to thinking it is a light or gloss issue on the LED screen. (Under a VNC connection I was able to work for hours on Xcode and some web browsing. )

Hope this helps.

Thanks.

Does your PC laptop have a glossy or LED display? If not then this ould be tough to draw conclusion from.

No, neither. But I was worried that it was simply a matter of squinting at the small text which would not have been an issue on my large desktop monitor. So this test has simply ruled out the size/fontsmoothing issue that I suspected.

Note that using the MBA direct causes a blinding headache for me within about 20-40 mins, so being VNC -ed in for hours without a problem on a similar sized screen indicates clearly to me that my eyes (for whatever reason ) simply doesn't cope with the MBA screen.

Hopefully rules out any messages which just say: test your eyes, or 'perhaps you are just getting older'.  Or 'any change of UI will do it'.

It could be. Some folks have sensitivity to display flicker, but that does not rule out others having issue with glare or content size issues, or combinations of these problems.

Just so we can clarify the term 'flicker' in this instance.

I believe what we are discussing is not the 'refresh rate'  - ie. 50 / 60Hz whatever, which you can adjust to an extent, and which TV manufacturers are pushing up to 120/240 etc through frame interpolation.

The issue here is PWM - Pitch Width Modulation, at a much higher INDEPENDENT frequency of around 400-500Hz, depending on the screen hardware.

The PWM is the killer. It affects subconsciously, and unfortunately with LED it is a much harder square wave - ie. ON / OFF, compared to the older variety which is a smoother 'analogue' style transition.

This is old news to hardcore gamers, who have been discussing monitors which are better/worse at this for some time. Presumably because the combination of large screen, close proximity, and fast action, leads to nausea more quickly.

FWIW I have no sensitivity towards 'refresh rate' - indeed I am perfectly happy watching a 50Hz TV, even though the indiividual frames are clearly seen, along with the usual 'flicker'. However most of the newer LED monitors are completly unusable for me, with a couple of exceptions.

Please Apple moderators/fanboys can we maintain differentiation between this important issue, and those who just don't like a glossy reflective screen or small fonts. Because those who have that sensitivity will have fixed their problems a long time ago, and won't be wading through 48 pages still battling with these nasty side effects.

If I have to believe in one theory, it would be this one Dan98

My old LCD monitor does flicker a little bit and I have no problem with that.

On the test page (http://www.lagom.nl/lcd-test/inversion.php), I can't see any flickering on my MBP.

So it should be something I can't see.

- I trust those who say it's not radiations (such as UV)

- So it's obviously something that moves really really fast, more than the flickering the test shows, that's what you and others call PWM.

Since it's a higher frequency than the flickering of old LCD's it sould not be a problem UNLESS the transitions between ON/OFF fluctuations are different.

So does anyone know a software which can remove PWM?

Sorry I didn't found the edit link...

Here is a good website that explains the issue:

http://www.squidoo.com/led-backlight-flicker

Then, according to this website (which is great as well)

http://vasyafromukraine.webs.com/

PWM (for dimming the screen) existed in older LCD but the new ones seem to have a lower frequency (in Hz) instead of kHz.

Don't forget to add  the fact that the fluctuations are squared.

PWM is a hardware-based modulation to prevent the need for a steady state current controller. It provides an easy approach to creating a linear response since light sources and other items like fans can have nonlinear responses to current. PWM "should" be fast enough to not be seen (ie, high Hz to KHz), but there may be details here that might cause it to be seen. For one, as dan98 suggested, if used at a low frequency then its square-wave nature may make it more prominent to some, similar to how a moving harsh edge in a video that does not have blurring effects might enhance the choppiness.

While PWM for a single light source should be fast enough to avoid detection, there also might be interference if the timing of the pulses for each pixel on a display are out of phase. Such a scenario might lead to a ripple-like effect as the frequencies go in and out of phase, that while still fast and not noticable to most, might enhance a problem for some. For example, if you have a gradient of output from one side of a screen to another, a gradual mismatch in PWM phase across the display even if running at 500Hz or higher might result in a pulsing as adjacent pixels go back and forth between turning on at the same time and turning on alternately. As a result, these pixels may together appear smoother followed by being more choppy, and also might pulse brighter and darker to a small degree.

This idea is just a guess, but may be a possibility why some displays might be more of an issue than others.

The thing that's inconsistent about PWM though, is that if you crank the display to its brightest (ie, put on a solid white color throughout the whole display) then there should be no PWM and therefore no adverse reactions. An easy way to test this would be to do this for a display that causes you discomfort to see if it lessens or goes away.

I'd be curious if those experiencing this are sensitive to CRT displays running at ~50-60Hz refresh rates. I'm personally very sensitive to this flicker, and could not use many older CRTs wtihout running them at 75Hz or higher, and imagine that if someone is sensitive to higher frequencies then these older screens would also have been a problem.

Topher,

Just to add to your text, I have read reviews of PWM-based LED monitors which unfortunately still rely on PWM at maximum brightness. Perhaps that is why I , and others, still suffer in this case.

Re. your last paragraph, subjectively for me CRTs at 50Hz are certainly flickery, and less pleasant than 75Hz for example. I wouldnt wish to spend all day long staring at a 50Hz CRT for that reason.

But the symptoms relating to PWM are in another league of discomfort altogether.

What can make it worse for me is that it is 'unnoticeable', in the sense that I can't actually SEE the PWM, rather it is 'felt'. I've no doubt this is why it has so far gone under the radar for most manufacturers.