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Eye strain from LED backlighting in MacBook Pro

There is one relatively serious con of the new LED backlit displays in the new MacBook Pros that seems to not get too much mention in the media. About a month ago I bought a new MacBook Pro to replace my standard white MacBook. One feature of the MacBook Pro that I was unaware of was the introduction of the LED backlit display to replace the CCFL backlight.

Once I started using my new laptop for long periods of time, I noticed severe eye strain and minor symptoms almost similar to motion sickness. After 20 or 30 minutes of use, I felt like I had been looking at the screen all day. Much longer and I would get headaches. If I used the old white MacBook (with its CCFL display), I had no eye troubles at all. Moreover, I could detect a distinct flicker on the MacBook Pro display when I moved my eyes across it - especially over high contract areas of the screen. White text on a black background was virtually impossible for me to read without feeling sick to my stomach because of all the flickering from moving my eyes over the text.

The strangest thing about all of this was that nobody else I showed the screen to could see these flickers I was seeing. I began to question my sanity until I did a little research. Discovering that the MacBook Pro introduced a new LED backlit display started to shed some light (so to speak) on what might be going on. I had long known that I could see LED flicker in things like car taillights and christmas lights that most of my friends could not see. I also knew that I could easily see the "rainbow effect" in DLP televisions that many other people don't see.

My research into LED technology turned up the fact that it is a bit of a technological challenge to dim an LED. Varying the voltage generally doesn't work as they are essentially designed to be either on or off with a fixed brightness. To work around this limitation, designers use a technique called pulse width modulation to mimic the appearance of lower intensity light coming out of the LED. I don't claim to fully understand the concept, but it essentially seems to involve very briefly turning off the LED several times over a given time span. The dimmer the LED needs to appear, the more time it spends in the off state.

Because this all happens so very quickly, the human brain does not interpret the flickers as flickers, rather as simply dimmer light. For most people that is. Some people (myself included) are much more sensitive to these flickers. From what I can tell, the concept is called the "flicker fusion threshold" and is the frequency at which sometime that is actually flickering is interpreted by the human brain as being continuously lit. While the vast majority of people have a threshold that doesn't allow them to see the flicker in dimmed LEDs, some people have a higher threshold that causes them to see the flickering in things like LED car tail lights and, unfortunately, LED backlit displays - leading to this terrible eye strain.

The solution? I now keep my screen turned up to full brightness to eliminate the need for the flicker-inducing pulse width modulation. The screen is very bright, but there are no more flickers and I love my MacBook Pro too much to exchange it for a plain MacBook with CCFL backlighting (which will also supposedly be switching to LED backlighting in 2009 anyway.) The staff at my local Apple store was of course more than helpful and was willing to let me exchange my glossy screen for matte even though I was beyond the 14 day return period. I knew that wasn't the problem though as my old MacBook was a glossy display. I've decided to stick with my full brightness solution. Sitting in a brightly-lit room tends to help alleviate how blinding the full brightness of the screen can be. In a dimly-lit room I guess I just wear sunglasses. Either way, the extreme brightness is worlds better than the sickening flicker I saw with a lower brightness setting

I would caution anybody considering buying a product with an LED backlit display to pay careful attention to make sure you don't have this same sensitivity. Turn the screen brightness down, find a high contract area of the screen, and quickly move your eyes back and forth over the screen. If you can detect the flicker, you may end up with this same problem.

I have no idea what percentage of the population has this sensitivity. I imagine we will hear more about it as more and more displays start using this technology. Hopefully the Apple engineers will come up with a way to eliminate this flicker some of us can see.

Russ Martin

15-inch MacBook Pro, Mac OS X (10.5.4)

Posted on Aug 23, 2008 8:25 AM

Reply
2,489 replies

Oct 16, 2017 4:33 PM in response to RMartin111

I will post this weekly, until someone from Apple responds. Bad news, people.


I own a 15' Macbook Pro 2015. From the beginning, my eyes hurt immensely. The black colours were too sharp and there was no way of making them softer (I tried everything, from using special apps, to recalibrating the screen).

After a month, I decided to buy a matte screen glare protector from Moshi. It helped a little, but the eyes still hurt.


After another month I've noticed that there are white soft spots on the screen (a monitor defect). I was still under warranty, so decided to get my screen replaced. Apple service center confirmed the problem with the white spots and replaced my screen.


And guess what? My eyes didn't hurt any more. The new screen is much softer to the eye. The blacks are not that sharp. No eye pain, no headaches.


My guess is that Apple uses screens from several suppliers. Each supplier provides a different screen quality. And I was lucky to get my screen replaced with the one from a good supplier.


This is a crazy lottery, people. Some people will get lucky and have proper screens right from the start. Some will get a worser screen and have problems.


Apple will not admit this. Because this defect covers at least 30% to 50% of all released macbooks. Replacing this amount of screens will make Apple go bankrupt.


My specs:

Macbook serial number: C0*******8WP

New screen model: 0000A02F

I think my old (bad) screen model was: 0000A02E


If you have headaches, you can look you screen serial number under System Preferences -> Displays -> Color -> Color LCD -> Open Profile -> Scroll to bottom to 'mmod' and look at 'Model' below.

User uploaded file


<Personal Information Edited by Host>

Oct 17, 2017 6:12 AM in response to ethan1el

If changing the LED screen alone has fixed the problem, is it possible that a third source of flickering, other than PWM and dithering, which is called inversion, is in play here? 😐😮



The following is from that link,

In a pixel on an LCD monitor, the amount of light that is transmitted from the backlight depends on the voltage applied to the pixel. For the amount of light, it doesn't matter whether that voltage is negative or positive. However, applying the same voltage for a long period would damage the pixel. Do you remember how electricity decomposes water into oxygen and hydrogen gas in chemistry class? Similar things could happen inside the liquid crystals that are in the pixels.In order to prevent damage, LCD displays quickly alternate the voltage between positive and negative for each pixel, which is called 'polarity inversion'. Ideally, the rapid polarity inversion wouldn't be noticeable because every pixel has the same brightness whether it a positive or a negative voltage is applied. However, in practice, there is a small difference, which means that every pixel flickers at about 30 hertz. In order to make this less noticeable, pixels with positive and negative voltages are interleaved, such that on average the screen as a whole keeps the same brightness

Does it "click" on you reading what's on that site? Does it make sense?

The "pixel walking" (inversion flickering) won't appear like "walking" on retina screens since individual pixels too small to spot, overall it looks more like flickering!


Normally this inversion is not an issue at all, but yes manufacturers can screw it up big time if such is unfortunately the case.


I am not a fan of sharp blacks too!! They look so artificial , so "out of place"! we rarely, if at all, encounter such degree of blacks, such degree of burning contrast in every day life, I once thought it too that it is this blacker than black that was causing my eyes hurt, but I assure you it's not.


If the illumination is stable, a black is powerless to hurt you, but armed with "flash", it becomes a different story 😐

Nov 5, 2017 1:46 AM in response to Keynode

Here's a new episode from this flicker-hunting season::


A friend has an Acer notebook which has PWM setting in BIOS!!! Sounds too good to be true!! But that's after he suffered a good six months of eye strain until he bumped into a post that teaches how to unlock hidden advanced BIOS features for Acer notebooks. When unlocked, the specific item is under the Integrated Graphics sub menu, it's called Backlight Control which lets you select one of the following::


PWM inverted

PWM normal

GMBUS inverted

GMBUS normal


The default value is PWM inverted, he figured better get rid of anything that has the cursing letter "PWM" in it so he changed it to GMBUS inverted without consulting what the heck that is,…. and poof! The eye strain is no more.


Now some theory ::


  1. Maybe how wrong I was, I might have underestimated the PWM factor. Very probable that most panel/motherboard OEMs have certain kind of "PWM Interface"* embedded in BIOS/firmware, I believe this is universal to almost all laptop PC's and Mac's, and it is actually an "exception" that Acer allows user to gain such access to switch it off. (through "hack")
  2. If OEMs have this PWM Interface embedded in BIOS/firmware, the graphics vendor can write codes targeting it.
  3. The friend's Acer notebook is listed on notebookcheck site as PWM-free, obviously It doesn't mean PWM Interface is not onboard.
  4. As long as the Interface stays open, it matters not the panel is PWM-free or it has a fixed high frequency of PWM, because the software can easily take over and take control.
  5. Intel graphics driver, and/or Intel power management driver, should have full privileges to this PWM Interface, Intel drivers may deem it "handy" to use PWM for dynamic control of brightness and panel power if it has detected such interface, thus completely ignoring other methods.
  6. The frequency of PWM is probably dynamically adjusted too via the driver, when you watch full screen movie, the driver "sees" to it that one frequency band should be used, when you edit text or browse web pages (static content) another frequency band is used.
  7. Because the driver can communicate with the LED backlight through PWM Interface, a driver update can completely change how the lighting behaves if it deems such change convenient or energy efficient.
  8. External monitor has independent power cord so power saving is not a concern, it also has its own brightness mechanism, all of these data should be recognizable and later read by the graphics driver as the monitor plugged in, the driver shall then decide it's not its business to force PWM on it. (That said, I don't know if there is watertight evidence that the driver absolutely can NOT force PWM on external displays).
  9. With that being said, maybe it can be concluded if the monitor is eye-straining there must be a dithering source, unless the monitor on itself uses a very bad PWM for dimming.( I think that's a rarity)
  10. Apple should seriously consider adding PWM and Dithering checkbox to the display settings in a future update, it's not that hard to do. Night Shift is a good move, it shows Apple's concern over the health impact of excessive blue light from LED display is real. So why stop there, Apple? You have enough cash, please continue doing what's right for the customer!! This Eye Strain thing is real!


* "PWM Interface" (or PWM Programming Interface) is just a made up term, some or all of the above may be proven wrong, I'm evolving.

Nov 5, 2017 8:36 AM in response to Keynode

Keynode wrote:


10. Apple should seriously consider adding PWM and Dithering checkbox to the display settings in a future update, it's not that hard to do. Night Shift is a good move, it shows Apple's concern over the health impact of excessive blue light from LED display is real. So why stop there, Apple? You have enough cash, please continue doing what's right for the customer!! This Eye Strain thing is real!


* "PWM Interface" (or PWM Programming Interface) is just a made up term, some or all of the above may be proven wrong, I'm evolving.

You continue to address Apple in this 9 year old thread. Apple still is not here. This is a user-to-user technical help community, it is not a medical advice nor Apple questioning community.


If you want to contact Apple or provide Apple feedback you can use these links:

Contact - How to Contact Us - Apple

Product Feedback - Apple

Nov 5, 2017 9:39 PM in response to BobTheFisherman

Geez Bob!

Why do you keep searching keyword "Apple" in my post instead of trying to understand the context?

Am I addressing Apple? Call it whatever you want.

By the way is there anything in Terms of Use that says any suggestions to Apple on this forum is strictly forbidden?

I'm just a level 1 with 8 points, you're a level 6 plus 19,481 points, you do not get there by keep going off topic asking members to contact Apple do you?

Why not contribute something that is relevant to the discussion at hand, really Bob!

Nov 6, 2017 7:49 AM in response to Keynode

Keynode wrote:


Geez Bob!

Why do you keep searching keyword "Apple" in my post instead of trying to understand the context?

Am I addressing Apple? Call it whatever you want.

By the way is there anything in Terms of Use that says any suggestions to Apple on this forum is strictly forbidden?

I'm just a level 1 with 8 points, you're a level 6 plus 19,481 points, you do not get there by keep going off topic asking members to contact Apple do you?

Why not contribute something that is relevant to the discussion at hand, really Bob!

1. I'm not searching the keyword Apple, you are directly asking a question of Apple in your posts, "So why stop there, Apple?"

2. "Am I addressing Apple?" Once again, no you are not addressing Apple here. You are posting issues and questions that can not be answered or solved by we users in this community.

3. You can post suggestions as long as you like but they may go unheard by Apple as they do not use this community for product feedback. I provided the link for submitting product feedback.

4. No, I got the points by trying to offer helpful advice. One such piece of advice is to contact Apple regarding product feedback. It is helpful to know that continuing to complain about a product in a 9 year old thread is not helpful. Advising about how to get your feedback to Apple is helpful.

5. If by "discussion at hand" you mean the current discussion, there is no current discussion. This thread is 9 years old and your tactic of keeping it alive is obviously not working. Use the advice I provided to contact Apple. It is the only way they will hear you and possibly investigate/correct your issue.

Nov 6, 2017 8:29 PM in response to BobTheFisherman

1. Again I think you took the highlighted sentence too literally and ignored the context. And like you said since this is a user to user discussion board I have yet seen any user gets confused or complains about anything in my post.


2. So now you start to put yourself in the positions of all other users out there? How can you know it can or can not be answered or solved by users collective efforts if you do not allow it to be discussed.


3. "You can post suggestions as long as you like"....SO I CAN? Thank you!


4. You surely are helpful. No offense but several pages back you suggested me to see an eye doctor! I think that speaks enough volume about your helpfulness.


5. I have no "tactic" here, I'm here merely to share my own observations on this eyestrain issue because here's the official place for such purpose, I may have some greater enthusiasm though, if that is what "gets me in trouble" I will not apologize.


6. Again it's not for you to decide for me what is helpful or not helpful, thank you for your concern anyway!

Dec 12, 2017 2:44 PM in response to Keynode

You may not get anywhere with Apple here. I've had lengthy discussions with them about my first reaction- very severe, and they tacitly recognized the problem, but officially they'd tell me nothing.


Later my contact there called me to set up an interview in order to get the info "directly to the engineers" at Apple.


It was a frustrating and lengthy call, since he was obviously being coached as to what to ask, how to respond, what specific language to use, etc. Many long pauses, none answers, evasions. It was clear Apple was interested in getting details of my experiences. They know it's a problem. They know it only affects a percentage of the population, from mild irritation to severe migraines and vomiting. Who knows what they will do? If anything. They're the richest corporation on the planet for a reason.


Some people can't eat peanut butter, but this is fixable. I'd gladly pay a premium to get my professional life back. By refusing to officially acknowledging the problem and sharing what they know, Apple is hurting people who depend on their products.


That's their choice, but you wont get their attention here.


When Bob the Bot makes a snark: Yes, many of us have been to eye specialists. There's nothing wrong with our eyes. For most of us they're better than most. Whatever causes this - it's not known to the broader medical community. Little research is being done publicly. Most opthamologists aren't computer specialists.


This forum's purpose is to let people share info and realize it's not just them. So it's not for you is it? Bot.

Eye strain from LED backlighting in MacBook Pro

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