LED Screen and Headaches?

[Longwalker]

LED brake lights and cheaper LED flashlights use low frequency pulse width modulation techniques for dimming. When these lights are not lit to full brightness, they will flicker at rates that can make some people nauseous. The effects are similar to staring at an CRT monitor (or TV) with a very low refresh rate. It is the flickering that is the issue, not LED light per say.

If you are sensitive to low frequency flickering and you wind up with a LED backlight that uses low frequency PWM to control screen brightness, you will have problems when the screen is not at full brightness. You might be able to avoid the problem by running the screen at full brightness, but there's no assurance that the backlight dimmer will run the LEDs constantly even at full brightness.

There are ways to dim LEDs without inducing nausea in a percentage of the population, but device manufacturers are seldom prepared to spend the money.

[Jackboot]

I'm not so sure that PWM dimming is the culrpit. From the brief reading that I've done, PWM units for backlights in the Macbooks in question (link below) have a minimum refresh of 100Hz and maxes at 20KHz - even the lowest refresh seems too high to cause a problem with eye strain.

Is there documented problems with LED backlighting on non-Apple products? I can't find any. It seems that this may be an apple-specific implementation. Anyway, the results are not good for these Apple users: migraines and vomiting from a couple of threads I've read.

Here is a good read: Apple MBP LED eye strain

[Longwalker]

I'm not so sure that PWM dimming is the culrpit. From the brief reading that I've done, PWM units for backlights in the Macbooks in question (link below) have a minimum refresh of 100Hz and maxes at 20KHz - even the lowest refresh seems too high to cause a problem with eye strain.

It's not just the frequency but also the duty cycle. 50Hz at a 50% duty cycle is flicker free but 100Hz at a very low duty cycle can be perceptible under certain circumstances.

Having looked over that thread I'd say the issue is the psychotropic effects of flicker acting through the visual system. Certain flicker rates can have profound effects on people--altered moods, migraine headaches, or even epileptic seizures--and the Macbook effects are in line with this.

[Jackboot]

What are your thoughts on this being a Mac LED backlighting specific problem? When searching I can only find complaints about headaches from Mac owners.

Not surprisingly for Mac users, despite nausea, vomiting, and migraine headaches, the thought to switch to a different notebook doesn't seem to be an option in the discussions.

[Longwalker]

What are your thoughts on this being a Mac LED backlighting specific problem?

I have no idea if this is Mac specific or not.

[i5aac]

Well, I know that I get headaches from LEDs out in the real world: flashlights, brake lights, etc. So that aspect of LEDs causing headaches is definitely not Mac, or even laptop, specific.

However, it may be that I would only have a problem with the Mac implementation of LED backlighting, and that the Thinkpad LED backlight would be fine.

That said, there does seem to be a relatively sizable group of people who have problems with LED lights in general. If the problem does indeed manifest itself in laptop screens, we could have a real problem if LED backlighting becomes as ubiquitous as widescreen format displays.

Either way, I'm taking the safe route at this point, and ordering a T400 with the WXGA+ TFT screen.

[gpzbc]

I'm having problems with headaches and eye strain since the day that I got my new Dell XPS M1530. I love the computer but I might have to send it back because it is unbearable. I get headaches within 20 minutes of use. And prior to this I never got headaches. And I spend a lot of time on the computer since I am a researcher and a student.

There is another thread in this forum that talks about this problem. It is not just apple MBP. checkit out here: (I can't post urls on this site so I omitted the prefix.)

forum.notebookreview.com/showthread.php?t=285025

[i5aac]

Hmm, thanks for the feedback and link. This is definitely a problem and I wonder what laptop manufacturers are going to do about it.

I'm glad I didn't get the LED screen, especially since I saw a friend's new MBP. His screen appeared to flicker to me, but not to anybody else there.

The fact that an LED screen can be so uncomfortable (at least for people with eyes like mine), is enough to scare me off completely, even though the problem might not manifest itself in on a non-glossy T400 LED.

gpzbc's link with the prefix restored: Anyone else experiencing eye strain on M1530 LED LCD?

[gpzbc]

For all of you doubters out there. I replaced my LED screen for a non-LED screen and the eye strain headaches were gone instantly. 100% gone!
No doubt about it.

[gpzbc]

I just want to re-emphasize that I traded in my LED glossy screen for a non-LED glossy screen. My eye strain headaches were gone instantly and I have never seen them since despite the fact that I am still using a glossy screen.

Oh, and by the way, I went to the eye doctor recently and my eyes are approximately the same as they have always been.

There is no doubt that LED was giving me a miserable headache. Perhaps it was me and not all users will have the same reaction. But, with that being said, I would urge all to take caution with the new LED screens.