Eye strain from LED backlighting in MacBook Pro

Actually it's my understanding the MacBook Airs of today demonstrate PWM. I see the 27" NEC falls close to where I feel the 30" did!

I thought the MacBook Airs should demonstrate PWM too, as the video below proves the screen to be flickering by using some specialized equipments:

http://www.youtube.com/watch?v=NKJhHK0bjpw&feature=relmfu

However, the simple PWM test method that we are using seems to tell that the screen has constant light. (though we are not sure if the video above is testing the same MacBook Air model as @MuDaeBoJongShin)

Nevertheless, I wonder if the simple PWM test method is flawed in some way?

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I have used the method on a few devices and the "simple method" could detect even the littlest of flickers, such as when a TV using PWM was at full brightness and still flickering tiny bit.

But I'm pretty sure displays using PWM don't use "a little PWM" in a worst case scenario, meaning at lowest brightness (backlight), because as the saying goes "If you got it, flaunt it, baby!". 😉

The guy with the oscilloscope in that video does not tell which year model it is. The guy in the 240fps video says he's using the 2011 model.

I had absolutely no problems with a 2010 air which was the core2duo model but the 2011 with a core i7 was painful I look at. I haven't done the pwm tests yet.

Well the human test is every bit as important, after all. I think there's refreshingly little placebo effect among posters here. Like some of these videos demonstrate there are other ways of picking up evidence of flicker.

I do also wonder, in the spirit of how this thread started in the first place if other complications are things like how the light spectrum produced by LEDs is further removed from nature than that of CCFLs. After all the reason you'll never see them in the few remaining 30 inch displays is that for the purposes of true color accuracy they simply are too different. That said I think flickerless CCFL tubes are going to be more rare than flickerless LEDs. For instance, the reason Eric may have an easier time with the CCFL is that between duty cycles the blow is milder thanks to some afterglow, while LEDs are capable of virtually flat on/off. It's harder for manufacturers and customers to ignore and I think we see how Apple did after all set out to address backlash after 2008. Still, I wonder be it spectral, difficulty focusing through glossy reflections, or otherwise what else with the technology must affect some people? I just wish one company would realize suddenly to market flickerless as a selling point, but I doubt they could ever be prepared to be held to it.

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It's ironic how LG markets their passive 3D TVs and monitors using polarized glasses as "flicker free", while they still exhibit backlight flicker which is no better than the flicker of some higher frequency active shutter systems.

Well to be fair, and I am really not versed in 3D, aren't they referring to a specific 3D phenomenon? Like if I hold the Real D glasses in front of my a foot or more in a theater, I see them freakin' blink. Which isn't to say worn as intended there is a flicker issue in theaters, but perhaps at home on some displays.

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Most 3D TVs use active shutter technology, where the left and right lens of the glasses would alternatively be blackened as the TV displays the image for the left and right eye in rapid succession.

LG and Philips use passive glasses technology, you get to use the kind of glasses you get at the cinema. Each lens and the TV screen itself is polarized so each eye views only the even or odd numbered horizontal line of resolution.

But that's the catch, LG and Philips still use PWM as a dimming method. So active shutter glasses operating at 480Hz and backlight on a passive 3D TV still flickering at a few hundred Hz, I don't see the diffence. Hence I consider it ironic that LG advertises them as "flicker free".

P.S. RealD 3D technology uses only one projector to display 3D at the theatre. Each frame is alternatively polarized for the left and right eye, so there is flicker similar to active shutter technology, as one eye views the intended image while the other views black. IMAX uses two projectors.

Wow, I mean I did just find this highly annoying LG ad specifically touting no backlight flicker. You're sure they're blowing smoke? That would be a shame.

Guys I can't believe nowhere seems to have tested the Apple 27" for PWM, that I can find anyway. I'm thinking of just ordering one and finding out the hard way. That the iMac equivalent checks out is surely a good sign. Sitll, it won't really be an end to the hunt for a matte display. I'm also thinking of upgrading to a Canon S100 not only for being one of the best compact cameras ever, but also for its 240 fps feature. Does anyone have any more details on the 240 fps flicker test, or know if it's a bullet proof way of testing displays?

It's not bulletproof, I think. If the flicker is at a very high rate, it could be difficult to see.

It is the difference in brightness that is confirming the test in the videos I've linked to.

It's the method in the tftcentral article that I recommend using, especially with a bright, macro lens.

Of course, at first you could just wave your finger. If you notice flicker immediately, you don't need to do any further testing.

The LG ad is just talking about the glasses technology. I haven't tested any of LGs 3D monitors, but plenty of 3D TVs which all had backlight flicker and were touted as "flicker free".

At 48 seconds it seems to be on about CCFL tubes.

They seem to be comparing the flicker of old 50/60Hz flourescent lights with the flicker caused by 3D technology. Monitors use LED backlights anyway, and they probably still flicker at the rate comparable to higher end active shutter glasses systems.

Even more irony. :)

Passive system is still the best 3D TV technology, and better for the average consumer than lower end active systems. If it would be combined with a flicker free backlight I would nab one in a heartbeat, since I love 3D.

Hi everyone, I have made a bit more observation with the NEC CCFL display (MultiSync PA271W).

It is PWM / flickering at 175Hz as mentioned earlier, but it feels reasonably comfortable looking at it for one full day of work. I believe the reason is like what Pixel Eater says, CCFL has after glow which ease out the flickering effects, and thus feel more comfortable.

When I put the NEC screen to very low brightness when the flickering effect is most apparant, I would encounter similar (but much less serious) uncomfortable feeling as looking at my MacBook Air's screen (11" 2010). My eyes feels hard to focus and have mild headache after looking at it for a day.

The MacBook Air didn't exhibit any PWM when tested with the simple method.

However, I still believe it's PWM which causes the eye strains in the Mac display. I *guess* the reason why it appears there's no PWM in the MacBook Air is probably because it's flickering at the KHz range.

Say for example if the screen is PWM at 5 KHz, there should be 200 vertical lines when we take the photo at 1/25s with the simple PWM test method. The lines may be too close together that made us believe that to be a continuous light.

Just a thought.

I "guess" you're wrong. ;)

I wonder too if there's a basic quality difference in high end or professional tubes found in monitors demanding the most from their color accuracy. It could just be something better for looking at, though that is pure speculation. I personally believe while pwm is the most blatant detail in how a monitor will treat the eyes, there must be qualitative differences. What they are could be hard to know.

To be honest I seriously doubt the Air, of all things, is flickering at an impressive rate. I also would like to discourage the idea that a higher rate will be beyond perception and thus healther. Out of sight out of mind, I don't think so. Not that anyone has likely indicated that.