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~ PWM and 2015 line of TVs ~

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Offline Xerox

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~ PWM and 2015 line of TVs ~
« on: 09 November 2014, 07:28:39 PM »

Quote
As of 2012, most implementations of LCD backlighting use PWM to dim the display, which makes the screen flicker more acutely (this does not mean visibly) than a CRT monitor at 85 Hz refresh rate would (this is because the entire screen is strobing on and off rather than a CRT's phosphor sustained dot which continually scans across the display, leaving some part of the display always lit), causing severe eye-strain for some people. Unfortunately, many of these people don't know that their eye-strain is being caused by the invisible strobe effect of PWM. This problem is worse on many of the new LED backlit monitors, because the LEDs have a faster turn-on/turn-off time than a CCFL lamp.


Total interest in PWM topics on HDTVtest site : 15704 Views

"PWM and 2013 line of TVs" -  13995 Views
"Did you test Televisions in 2014 for Flicker Free ( no PWM ) ? like you promised" - 880 Views
"Check if 2015 TVs use PWM (if they are flicker free or not)" - 829 Views

Therefore i ask kindly the owners of HDTVtest.co.uk to include the simple PWM check to their basic test list for Televisions coming up next year, in 2015 and after that.

I can help with any methodology regarding the actual testing process.

Why HDTVtest needs this feature:

Because it will inform the readers of the site and forum members about the way the Television works from 0 to 100% brightness regarding PWM. ( pulse width modulation ) If television makers advertise their TVs as "life like" then no such flicker should exist.

Monitors of all major brands as of 2014 have transitioned to a Direct Current implementation that maintains the eye - brain system in a state of relaxation.

However no information exists regarding Televisions. Testing this will be a welcomed and important addition for everyone.

If the television is PWM free ( flicker free ) then the reader can make a more correct choice when buying a new TV in order to avoid eye strain and headaches caused by the invisible strobe effect of PWM.

Quote
Of course the problems which can potentially be caused by the use of PWM are not seen by everyone, and in fact I expect there are far more people who would never notice any of the symptoms than there are people who do. For those who do suffer from side effects including headaches and eye strain there is an explanation at least.


Testing this will make companies react like they did with monitors.

http://www.tftcentral.co.uk/articles/pulse_width_modulation.htm

http://www.tftcentral.co.uk/articles/flicker_free_database.htm

Quote
The effect can be subtle. You might not notice it on a conscious level. The most revealing aspect of this for me personally was a time when I used two flicker-free monitors side-by-side for a period of 2-3 months. Afterwards, I tried to switch one of them back to a non flicker-free monitor, but simply couldn't do it. I felt the effect after a few days.


http://www.flatpanelshd.com/focus.php?subaction=showfull&id=1362457985

Thank you !
« Last Edit: 17 November 2014, 03:42:47 PM by Xerox »

Offline Xerox

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Re: ~ PWM and 2015 line of TVs ~
« Reply #1 on: 17 November 2014, 11:06:08 AM »
Hello.

Any official answer from the reviewers or owners of HDTVtest.co.uk regarding my request ?

Offline Xerox

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Re: ~ PWM and 2015 line of TVs ~
« Reply #2 on: 17 November 2014, 03:32:41 PM »
Hello.

Any official answer from the reviewers or owners of HDTVtest.co.uk regarding my request ?


Since HDTVtest.co.uk reviewers / owners are obviously ignoring my request i will try to provide myself the results to those that read my posts. Hopefully HDTVtest.co.uk reviewers / owners will change their mind and give me an answer with yes or no if they are going to test this PWM in 2015. (so i don't waste any more of my life on this topic on this site)

Official answer from an expert :

Quote
For PWM, you can already deduce it from our pictures of motion blur. If you see a continuous blur, it doesn`t use PWM.

All TVs of 2014 : http://www.rtings.com/info/motion-blur-tvs

Here is what to look for:

Very low frequency: http://www.rtings.com/images/reviews/w600b/w600b-impulse-medium.jpg

Low frequency:  http://www.rtings.com/images/reviews/h6350/h6350-motion-blur-medium.jpg

Mid frequency: http://www.rtings.com/images/reviews/h7150/h7150-motion-blur-medium.jpg

High frequency: http://www.rtings.com/images/reviews/w850b/w850b-motion-blur-medium.jpg

All, except the first, are calibrated at the same brightness (100cd/m2). The PWM shows on these pictures because the camera is moving (on a rail) when taking these pictures. If the camera was static, it wouldn’t have showed up. The distinct superposition would have been due to the frame rate instead.
« Last Edit: 17 November 2014, 03:43:54 PM by Xerox »

Offline FoxHounder

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Re: ~ PWM and 2015 line of TVs ~
« Reply #3 on: 17 November 2014, 03:58:50 PM »
I guess it's obvious that no answer from the representatives means they don't see this feature as absolutely necessary in every review.
I'm pretty sure that David or Vincent will point out if there are really some PWM-induced problems in certain TV set, otherwise it's not even mentioned in review. Seems fair to me. Why waste precious time on something, if you can put it into really meaningful chapters of review?

It's only my personal opinion, don't take it as an Official Licensed HDTVtest™ Answer®Ⓒ.
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Offline Xerox

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Re: ~ PWM and 2015 line of TVs ~
« Reply #4 on: 18 November 2014, 03:00:26 PM »
I guess it's obvious that no answer from the representatives means they don't see this feature as absolutely necessary in every review.
I'm pretty sure that David or Vincent will point out if there are really some PWM-induced problems in certain TV set, otherwise it's not even mentioned in review. Seems fair to me. Why waste precious time on something, if you can put it into really meaningful chapters of review?

It's only my personal opinion, don't take it as an Official Licensed HDTVtest™ Answer®Ⓒ.

The problem is that PWM produces : visible flicker, eyestrain, eye fatigue, headaches and other associated issues for people sensitive to it.

Obviously some people are blind to it or have reduced and weak sensation in their cells thus no proper perception of their actual environment.

Quote
The flicker itself in display backlights may be subtle and not easily perceptible for some people, but the natural variation in human vision seems to make it clearly visible to others. With the use of high-brightness LED's on the rise it is becoming increasingly necessary to use short PWM duty cycles to control brightness, making flicker more of a problem. With users spending many hours every day looking at their monitors / TVs, shouldn't we consider the long term effects of both perceptible and imperceptible flicker?

Offline Vincent

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Re: ~ PWM and 2015 line of TVs ~
« Reply #5 on: 18 November 2014, 03:49:46 PM »
The problem is that PWM produces : visible flicker, eyestrain, eye fatigue, headaches and other associated issues for people sensitive to it.

Can you please provide some statistics on what proportion of TV viewers are affected by this issue? I've never ever encountered any complaint from anyone except you in my 7 years of reviewing TVs.

Warmest regards
Vincent

Offline Xerox

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Re: ~ PWM and 2015 line of TVs ~
« Reply #6 on: 18 November 2014, 11:55:04 PM »
The problem is that PWM produces : visible flicker, eyestrain, eye fatigue, headaches and other associated issues for people sensitive to it.


Can you please provide some statistics on what proportion of TV viewers are affected by this issue? I've never ever encountered any complaint from anyone except you in my 7 years of reviewing TVs.

Warmest regards
Vincent


Hello Vincent,

Let's say for a moment you are right and this is a non issue.

If we look at history of TV/monitors there was a transition from CCFL to LED.

http://www.tftcentral.co.uk/articles/pulse_width_modulation.htm (here you find a splendid explanation)
http://www.tftcentral.co.uk/articles/flicker_free_database.htm

When people started to accuse visible flicker, eyestrain, eye fatigue, headaches. (reactions of the body to unconsciously or in many cases as statistics showed to consciously perceived stimulus) some companies like AOU/BenQ identified the problem and provided the solution by removing PWM from 100% brightness all the way down to 0% brightness.

Others like Japanese EIZO started first using monitors that were marketed as flicker free with "hybrid solution", meaning no PWM down to 20% brightness.

BenQ was then quite quickly followed by Samsung & LG that felt that they were badly positioned by BenQ marketing in terms of potential customer healthcare issues.

So now we know for sure that all good monitor makers including Samsung & LG understood that yes there was a health issue. And they addressed this problem. But not before people started to complain. (BenQ was clearly a step ahead here). And Samsung & LG only after BenQ marketing was hurting them.

Reviewers that tested if monitors used PWM or not definitely proved the facts and forced all monitor makers to change their flickering LED back lights.

The exact same issues that were present on monitors when they changed from CCFL to LED are now present on TVs. (and statistics regarding health issues & unhappy users apply the same to TVs). But since here the companies encountered more ignorant reviewers (not pointing out this), they did not change anything, for 2014 at least.

There are only positive aspects to flicker free screens. The response time of the panel and the input lag are simply the same as proved by all flicker free monitors tests - from professional to gaming, from IPS to VA to TN.

I myself can definitely perceive this flicker when present and i was able to do so weather they were monitor screens or TVs.

Long term effects of both perceptible and imperceptible flicker definitely exist and the brain records it, usually in an unconscious way and the the body reacts accordingly. ( just as it reacts over long time exposure to cordless phones radio stations sitting close to you, or strong wireless internet stations )

If you check for PWM and state this in your reviews the companies will most likely do what they did with their monitors when they quickly changed the implementation when people started to accuse visible flicker, eyestrain, eye fatigue, headaches.

This problem affects all LED TV owners. The flicker is real, it's there and it sucks. If you ever used a PWM free LED screen and tried to go back to flickering screens you would know what i mean. And calibrated TVs are never near the top end of their brightness where the flicker gets very intense but less perceivable, so it affects many.

I think you would do something that would benefit the people by stating in your reviews if the screen is PWM controlled or not. I strongly advise you to do this since it is also very easy to check.

And to answer your original question once more, i am also sure you never heard anyone complain about PWM flickering LEDs until some experts made the complains of the people public.

Once the problem becomes well known, nobody denies it you know. I am sincerely complaining about this issue. Please look into it.

Warmest regards
« Last Edit: 19 November 2014, 12:00:57 AM by Xerox »

Offline FoxHounder

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Re: ~ PWM and 2015 line of TVs ~
« Reply #7 on: 19 November 2014, 06:52:59 AM »
If you check for PWM and state this in your reviews the companies will most likely do what they did with their monitors when they quickly changed the implementation when people started to accuse visible flicker, eyestrain, eye fatigue, headaches.
We're absolutely running in circles here. We've discussed these PWM so much that these endless topics give me a headaches, not PWM.
Try to cope with 2 things:
1) Modern electronics use impulse modes everywhere, most manufacturers won't ditch PWM because it's more handy in schematics and helps to save some energy. It's a very strong argument industry-wise.
2) People lived with CRT technology with strong flicker for many decades, and they didn't suffer as you tell, except for a small minority of viewers.
Looks like nobody is so "concerned" except for a few reviewers and their fanatic followers. This issue was around with any LED backlight, yet for some years people lived happily with PWM backlight control on TVs. Then around 2010 some dudes started to shout at every corner, because of poor PWM implementation on cheap PC monitors. What does it even have to do with TVs? :chin:

I urge you to stop flooding the forum with these same posts about PWM, evil corporations and such.
I think, a few threads are more than enough for this. This is getting too old now.
« Last Edit: 19 November 2014, 06:57:50 AM by FoxHounder »
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Offline Xerox

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Re: ~ PWM and 2015 line of TVs ~
« Reply #8 on: 19 November 2014, 03:04:38 PM »
If you check for PWM and state this in your reviews the companies will most likely do what they did with their monitors when they quickly changed the implementation when people started to accuse visible flicker, eyestrain, eye fatigue, headaches.
We're absolutely running in circles here. We've discussed these PWM so much that these endless topics give me a headaches, not PWM.
Try to cope with 2 things:
1) Modern electronics use impulse modes everywhere, most manufacturers won't ditch PWM because it's more handy in schematics and helps to save some energy. It's a very strong argument industry-wise.
2) People lived with CRT technology with strong flicker for many decades, and they didn't suffer as you tell, except for a small minority of viewers.
Looks like nobody is so "concerned" except for a few reviewers and their fanatic followers. This issue was around with any LED backlight, yet for some years people lived happily with PWM backlight control on TVs. Then around 2010 some dudes started to shout at every corner, because of poor PWM implementation on cheap PC monitors. What does it even have to do with TVs? :chin:

I urge you to stop flooding the forum with these same posts about PWM, evil corporations and such.
I think, a few threads are more than enough for this. This is getting too old now.


1. You are contradicting yourself. All monitor makers this year finally ditched PWM the second they acknowledged the fact that it produces perceivable health issues when combined with LED. These are clear facts.

2. CRT flicker is quite different, although it also makes you tired.

I would not call experts as "reviewers with fanatic followers."

I am waiting for an answer from the reviewers on hdtvtest.co.uk that actually test the models not from forum moderators. Read my previous post Vincent.

Quote
You should investigate more before posting uninformed articles. The human eye is used to natural light which is flicker-free, for example some people get head aches from ceiling fluorescent lighting which is a flicker lighting(most of them flicker at the same frequency as the AC current).
« Last Edit: 19 November 2014, 03:06:36 PM by Xerox »

Offline SETEM

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Re: ~ PWM and 2015 line of TVs ~
« Reply #9 on: 19 November 2014, 04:09:00 PM »
Just to add my two cents...

I always thought it was commonly known that CRT's (most of which ran at 50 Hz and 60 Hz) could cause headaches and eye strain after long sessions. And that flickering lights, whether the flicker is perceivable or not, can induce headaches. My parents always used to say "shouldn't you take a brake from the game now? It's not good for your eyes, and you'll get a headache...", and I can sometimes find some types of lighting somewhat annoying. I almost never got a headache from playing the old NES, N64 etc. no matter how long I played for, although some of my friends sometimes used to say they "needed a brake" because of it.

That being said, that's all there ever was to it as far as I have been concerned - after a while, some people got a headache from watching the TV, they took a break, and then they were fine...

Yes, this whole PWM thing might be more of an issue for more people when it comes to PC monitors, as they are for a different use than TV's. Comparing a PC monitor to a TV, the viewer is likely to sit closer, perhaps in a less ergonomically "correct" position, while doing work which might otherwise be tiring in itself. Headaches are AFAIK only symptoms of parts of the brain being overloaded with stimulus, whether that stimulus is otherwise noticeable or not. A flickering screen might make things worse quicker, yes, but the TV market/usage probably isn't comparable to the PC monitor counterparts. You sit (or even lie down) on a couch and relax/enjoy yourself, and most people probably don't expect to be seated in front of their TV for 8 hours straight on a daily basis, like you may have to at work. Monitors and TV's have different purposes, and are built accordingly.

I don't see the point in testing TV's for PWM if it's only going to take up more time, and yield "PWM: Yes. Headaches: No. Eyestrain: No. Nausea: No. Death: Yes, the PWM killed Vincent because it was amplified by his glasses!" 99 % of the time - Especially not if nobody seems to have a real problem with it (outside of what I've mentioned, when people usually just take a break).

That's what I think, anyway.

(PS: Just kidding, Vince, your glasses are cool 8) ;D )
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Offline FoxHounder

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Re: ~ PWM and 2015 line of TVs ~
« Reply #10 on: 19 November 2014, 04:58:44 PM »
1. You are contradicting yourself. All monitor makers this year finally ditched PWM the second they acknowledged the fact that it produces perceivable health issues when combined with LED. These are clear facts.
I'm pretty sure that any company engineer is aware of PWM. Because they... err... design this stuff.
Monitor makers replacing PWM with DC driving is a marketing game, nothing more. Trying to link this with some camera geeks exploring PWM is a wishful thinking.
Wait 'till they introduce a scanning backlight all over again to fight the smearing.

2. CRT flicker is quite different, although it also makes you tired.
The only difference is a vertical scan with phosphor afterglow.
If the CRT wasn't so bad, why suddenly PWM generates so much buzz on the forums?

You should investigate more before posting uninformed articles. The human eye is used to natural light which is flicker-free, for example some people get head aches from ceiling fluorescent lighting which is a flicker lighting(most of them flicker at the same frequency as the AC current).
Here's something informative: any light (and I mean ANY) is a beam of photons, which oscillate with a certain frequency. Every light literally "flickers" on a particle level. Let's ask Mother Nature to revise its laws, because life can give headaches and everyone eventually dies.
« Last Edit: 19 November 2014, 05:00:35 PM by FoxHounder »
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Offline Xerox

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Re: ~ PWM and 2015 line of TVs ~
« Reply #11 on: 19 November 2014, 06:07:49 PM »
You are wrong FoxHounder ! What you are doing twisting my words is called manipulation.

Light from the sun does not flicker. And your eyes adapted to the natural environment and so they are used to natural light which is flicker-free.

That is why many people can detect when lights actually flicker. Because their eyes perceive light as something constant and persistent. ( a  continuous flow )

That is also why people can "feel" higher refresh rates. Because their eyes see continuously not in frames per second.

http://www.100fps.com/how_many_frames_can_humans_see.htm

Quote
Maybe 120fps is enough, maybe you will get headaches after 3 hours. Seeing framewise is simply not the way how the eye\brain system works. It works with a continuous flow of light\information. (Similar to the effects of cameras' flashlights ("red eyes"): flashing is simply not the way how we see). So there are still questions. Maybe you need as much as 4000fps, maybe less, maybe more.

The same question as for fps will arise for resolution. How many pixels can the human eye see? Does 2000x1000 (=Star Wars Episode II resolution) look like reality? Or is it just enough to make a film "cinemable"?


Quote
It depends on whether the incandescent light is powered by Alternating Current (AC) or Direct Current (DC):
    DC: no flicker
    AC: no perceptible flicker because the decay time of the incandescent filament (the time it takes the filament to cool off and stop emitting energy) is longer than typical current frequency (50 or 60 Hz)."
« Last Edit: 19 November 2014, 06:13:44 PM by Xerox »

Offline Xerox

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Re: ~ PWM and 2015 line of TVs ~
« Reply #12 on: 20 November 2014, 09:02:38 PM »
If you use a fast shutter camera you can clearly see this annoying flickering of the back-light.

This is PWM :

https://www.youtube.com/watch?v=LWlNTnxooA8

I can see it without the need of a camera ( of course not that intense ) but it's definitely there for me.

Offline Xerox

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Re: ~ PWM and 2015 line of TVs ~
« Reply #13 on: 21 November 2014, 04:11:57 PM »
Here enjoy more PWM on laptops screens this time : https://www.youtube.com/watch?v=IHKWQRzS2tE

This is what you actually experience with your own eyes : https://www.youtube.com/watch?v=_4j6a_FLYIs

But this is what is actually happening behind : https://www.youtube.com/watch?v=GsopXyXJ91E

So what you see here on this Samsung 4k LCD LED TV is PWM not refresh rate : https://www.youtube.com/watch?v=LWlNTnxooA8

If you want proof, then simply use a fast shutter camera on any non-pwm screens and the refresh rate won't show up !

Here proof :  https://www.youtube.com/watch?v=1CNOIbmUws0

Offline Xerox

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Re: ~ PWM and 2015 line of TVs ~
« Reply #14 on: 22 January 2015, 12:09:05 PM »
Don't forget to test PWM for 2015 models. Thanks.