Is flicker free tech actually "bad" for eyes?

[bobert50]

I've had a Benq xl2411z for a while now and before it I had a Benq xl2720z.

While both have been very responsive monitors that are faultless generally, it feels like they made me really dizzy somehow?! Best way I can describe it is almost really bad motion sickness.

However, I have never experienced this on any other older monitor that I have ever owned, including the monitor I am now using again, which is the LG W2363D-PF. All of these have been PWN, which of course could be just total coincidence.

Would anyone have any idea what is going on? am I just strange?! has anyone else noticed similar? am I the only one out there? I thought I'd write a thread on it just in case I am not!

Reading the internet suggests the latest flicker free tech is actually supposed to be better, but perhaps not for everyone? I'm really confused about this issue right now.

Any help is very appreciated

 

[theaterix]

Monitors in general are bad for your eyes, especially when your like me and you literally don't have to blink... Not good lol!

 

[aatu]

1) You don't happen to have ULMB, Active 3D or anything of the sort enabled? As those features directly defeat the whole purpose of PWM-free backlight.
2) Does the dizziness happen only while gaming, or all the time?
3) How high is your brightness? If it's too low, you have to exert your eyes to see properly, while a too high can also make your eyes more tired faster.
4) How good is your eyesight? Are you sitting too far or too close, perhaps? For computer usage, I think a viewing distance of 1.0-1.5x of the diagonal of the monitor is recommended.
5) How bad is the TN's color invertion from your viewing position? Are there any reflections or glares on the screen while you're viewing the monitor? These things can decrease your immersion, as your brains need to do extra work.

But all in all, I don't remember DIZZINESS being a common symptom. Tired eyes and headaches are the most quoted symptoms for PWM backlight. And motion blur is usually the most quoted downside of the PWM-free backlight. I don't remember dizziness from either side. Motion sickness is a symptom among 3D viewing, though.

 

[eddiew]

Surely what's being touted as "flicker free" this year is just "how TFTs were" 10-12 years ago? I was an early adopter of TFT specifically because the backlight didn't flicker and thus didn't give me headaches like CRTs did. Felt like a real step backwards the first time I saw a strobing backlight as a 'feature' of an LCD screen.

That aside, all I can think of is input lag... if you feel like there's a delay between your keyboard/mouse input and things happening on screen, that could mess with your equilibrium.

 

[aatu]

@eddiew:

Indeed, the first CCFL TFTs didn't flicker as much as the modern LED TFTs, or even the then-ubiquituous CRTs. The CCFL's native flicker was around the kHz range, very hard to notice with a naked eye. At some point someone invented a good way to reduce power draw and simultaneously control the brightness more easily, by switching the backlight rapidly on and off with PWM, around 150-300Hz. For CCFL, it wasn't so bad, as the CCFL has a "cooldown" period, meaning the backlight didn't have enough time to turn completely dark, in any case. (CRTs had the same benefit, btw)

But the problem arose when the LED backlights came, because during that change, the manufacturers didn't bother to adjust the PWM. LEDs have a very fast on/off rise time, so the flicker became more evident. Even 150Hz means it's still fairly hard to notice the flicker by eyes alone, but the people's nerve systems could detect it, nevertheless. And this caused headaches and tired eyes.

The ugly part:
I read somewhere, that there's actually nothing stopping manufacturers from using the PWM at a kHz range, apart from price. IIRC, the circuitry/components driving the PWM at a kHz range would cost less than 50 cents more compared to the 150Hz range. Yes, 50 cents is a lot when those costs start adding up. But those that know of this matter and are affected by it, will rather go for the models that cost 50€ more. So the manufacturer that saves the 50 cents, loses the sale to another manufacturer, who IS taking this into consideration.

Not sure how much the modern PWM-free technologies cost. As I'm assuming it's not just a case of "not using PWM". From what I've understood, with CCFLs it was possible to simply decrease the voltage linearly to decrease the brightness. With LEDs, this is not possible (well, it is possible, but in a very small scale). The PWM method made it easier for both LED and CCFL to control brightness and power draw. PWM is also focusing on controlling the voltage, but like said, it turns it on and off very rapidly, instead of directly decreasing it. For modern LEDs the PWM-free method is apparently decreasing the current, instead. This calls for a different type of circuitry. If someone has more info on that one, I'd be happy to hear it, as I'm not that familiar with it.

As for the input lag:
Yes, that could indeed be a possible cause for dizziness. Although, I would reckon that especially the gaming monitors would have a low input lag.

Ps. Sorry for the excess rambling, got a little carried away.

 

[eddiew]

Ps. Sorry for the excess rambling, got a little carried away.

Not at all, that was quite interesting I will definitely be looking for "flicker free" on any future monitor purchase. Just kind of assumed it was normal for them to be that way... maybe my old-but-expensive Dell 24 has spoiled me :S