Talk about TVs, including LCD, LED, plasma, and OLED. Ask for buying advice or whatever you need help with.
By proyal
#7155 Hdtvtest mentions flicker on BFI (black frame insertion is used only in Samsung & Sony) : http://www.hdtvtest.co.uk/news/ue65js95 ... 234012.htm

This BFI flicker is different from PWM induced flicker ?

The PWM test is very simple to do by selecting a faster shutter speed on the camera.

The only problem is how are you going to differentiate in case there is both PWM and black frame insertion induced flicker ?

These two should be different but ....

"Strobing, by its nature, is PWM. Simple black frame insertion (via backlight) is a very simple form of PWM that is synchronized to the refresh rate, not used for dimming, but used for motion blur elimination."

So PWM is used as black frame insertion on Samsung and Sony models by default ? Panasonic and LG also use a partial back-light scanning so PWM is necessary in those cases ?

The monitors without PWM are really relaxing because you can lower the brightness and have absolutely no flicker, unfortunately this is not the case with TVs, because the panels use PWM and since they were very slow panels up until 2014 Sony models came up, they needed this PWM Strobing in the form of PWM to compensate.

Maybe 2015 1080p models will be much faster and no longer need PWM.

BFI as stated in the bold paragraph is synchronized to the refresh rate, not used for dimming so both PWM and BFI should exist at the same time ?
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By Rasmus Larsen
#7157 I started using PWM free LCD monitors on my desktop shortly after the first models were released and I would never return. I can sit in front of the monitors for a full day without eye strain. That was certainly not possible before. I tried switching back to another monitor with PWM control for a few weeks and clearly felt the difference.

But yeah, I guess you could call BFI a form of PWM, but it is also important to think of the methods as separate to fully understand it. BFI is controlled by switching the backlight on and off in sync with the refresh rate. This is intentional to reduce blurring. PWM is happening constantly because it is how TV manufacturers control brightness of the LEDs and consequently the TV panel. You can easily eliminate BFI just by switching it off in the menu, but you can never get rid of PWM in a LCD TV unless you run at 100% brightness (and even then some TVs continue to use PWM).

I have little hope that TV manufacturers will eliminate PWM and other types of flicker on TVs. Most consumers are simply not aware of this and manufacturers don't care.

In my opinion we need a couple of things to solve this such as an OLED panel driven by the sample-and-hold method. That is how LG is doing it. However, to eliminate blurring we need the entire industry to move to much, much higher frame rates than 24, 25 and 30fps. Preferably 120fps or higher, and preferably with adaptive sync systems where the source and TV panel are always in perfect sync.

Just my take on it :)
By proyal
#7166
Rasmus Larsen wrote:I started using PWM free LCD monitors on my desktop shortly after the first models were released and I would never return. I can sit in front of the monitors for a full day without eye strain. That was certainly not possible before. I tried switching back to another monitor with PWM control for a few weeks and clearly felt the difference.

But yeah, I guess you could call BFI a form of PWM, but it is also important to think of the methods as separate to fully understand it. BFI is controlled by switching the backlight on and off in sync with the refresh rate. This is intentional to reduce blurring. PWM is happening constantly because it is how TV manufacturers control brightness of the LEDs and consequently the TV panel. You can easily eliminate BFI just by switching it off in the menu, but you can never get rid of PWM in a LCD TV unless you run at 100% brightness (and even then some TVs continue to use PWM).

I have little hope that TV manufacturers will eliminate PWM and other types of flicker on TVs. Most consumers are simply not aware of this and manufacturers don't care.

In my opinion we need a couple of things to solve this such as an OLED panel driven by the sample-and-hold method. That is how LG is doing it. However, to eliminate blurring we need the entire industry to move to much, much higher frame rates than 24, 25 and 30fps. Preferably 120fps or higher, and preferably with adaptive sync systems where the source and TV panel are always in perfect sync.

Just my take on it :)


Thank you for your reply.

Is your monitor a BenQ GW2760HS ? That was the first one i think.

They could eliminate PWM that controls brightness but you would still have BFI which may be even more visible than PWM ?! CRT style ?

It's really sad ... monitors don't use PWM or BFI and can display perfectly fine video. Why can't they do the same with their TVs lineup.

It was the marketing that BenQ used that forced other companies like LG/Samsung/Asus/Dell .etc to adopt PWM free monitor models.
By proyal
#7168 Here is what to do if you can test the 1080p models of 2015. (since 4k models will be around 20ms input lag and still require some BFI or like HDTVtest suggested :

If you’re sensitive to flicker and cannot put up with [LED Clear Motion], our favourite compromise is adjusting [Blur Reduction] to “8” and [Judder Reduction] to “0” after setting [Auto Motion Plus] to “Custom“, which improves motion definition without causing SOE.


)


So :
Disable BFI on Sony & Samsung and back-light scanning on the rest (Panasonic / LG .etc)

Use a fast shutter camera speed to check for PWM (that controls the brightness)

If the panel itself is fast enough like monitors with AOU VA then there is absolutely no need for BFI. That means only PWM is left as the offender.

Try to test for PWM with the BFI/BLS off. This should answer all questions this year.

Thank you.
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By Rasmus Larsen
#7170
proyal wrote:Is your monitor a BenQ GW2760HS ? That was the first one i think.


One BenQ and one Eizo :)

Luckily, BFI is rare on PC monitors, but some gaming monitors use it in the game mode. I've noticed more and more monitor manufacturers advertising "flicker free" monitors so at least for monitors we are heading in the right direction.

I will probably do some PWM testing on TVs this year, yes. Here's our write-up on the subject and how we use a camera to test for PWM: http://www.flatpanelshd.com/focus.php?s ... 1362457985
By proyal
#7186 1. BFI is a software trick :

http://www.testufo.com/#test=blackframe ... qualizer=1

" Motion blur reducing strobe backlights (e.g. LightBoost) puts black periods between frames, and is more efficient than this software-based black frame insertion. "


2. BFI can be turn off and some models behave better than other with it off.

http://www.rtings.com/info/motion-blur-tvs

Sony W850 (60"/70") has the best looking non BFI motion blur last year. Moreover Rtings confirmed to me that W850 didn't use PWM or it had a very high frequency one !

BFI off : http://www.rtings.com/images/reviews/w8 ... medium.jpg
BFI on : http://www.rtings.com/images/reviews/w8 ... medium.jpg (but flicker CRT style)

Samsung H7150 usage of PWM : http://www.rtings.com/images/reviews/h7 ... medium.jpg

Where to look for PWM on H7150 above image : http://s14.postimg.org/isgcciiy9/Test.jpg

Other examples of PWM :

Very low frequency: http://www.rtings.com/images/reviews/w6 ... medium.jpg

Low frequency: http://www.rtings.com/images/reviews/h6 ... medium.jpg

Mid frequency: http://www.rtings.com/images/reviews/h7 ... medium.jpg

High frequency: http://www.rtings.com/images/reviews/w8 ... medium.jpg

3. 60 Hz monitors / TVs with refresh rate/input lag of 8 ms are blur free to us just like a CRT because our own eye blur masks around 8 ms of lag. What Sony needs to do is get panels that are under 10 ms this year. Not all transitions are that fast but at least faster and closer to the golden 8 ms where eyes can't distinguish the blur.

120Hz screens need 4 ms refresh rate/input lag to behave like CRT to our eyes.

A 60Hz display with 8ms refresh rate/input lag would feel like a fluid experience without any motion blur to our eyes and a 120Hz display would need 4ms refresh rate/input lag to be as fluid as the 60Hz 8ms one (motion blur less) ?


It most certainly wouldn’t feel like a fluid experience with no motion blur to our eyes. It’s just that the motion blur from our eyes would mask the 8ms pixel response of the monitor. The reason that figure needs to be 4ms for 120Hz is that the motion blur is lower at higher refresh rates – so an 8ms pixel response in that case would be visible beyond the motion blur from our eye movement. It is explained a lot better in the article.
By proyal
#7190 Made small mistakes.

BFI helps hiding the low frame rate issue (like 24 fps broadcasting/bluray with sample and hold), even if the response time was 0ms. But it introduces flicker.

If the frame-rate of the content is 48 fps or 60 fps like when you use the TV for games then BFI is less useful just like on 60Hz monitors with fast 8 ms panels and 60 Hz content.

http://www.rtings.com/info/motion-blur-tvs

Moreover here is where you need to look for PWM :

W800b didn't use PWM in 2014 ! : http://postimg.org/image/dlk5fcz2x/
H6400 did : http://postimg.org/image/c2xy1v7a1/
H7150 did : http://postimg.org/image/4hfoaayll/

Do you understand ?
Attachments
h6400.jpg
h7150.jpg
w800b.jpg
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By Rasmus Larsen
#7247 PS: Will report on the LG UF8500 and Panasonic CX6 that we have on the test bench shortly.

As well as other future TVs.
By proyal
#7248 That is fantastic work.

I hope to buy a TV that is PWM free this year. Best chance is Sony but we have to wait and see what panels they use from AOU.
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By Rasmus Larsen
#7281 Same for LG UF8500 and Panasonic CX6. Both use PWM at a frequency of 125 Hz.
By proyal
#7350 Last year W700B / W800B from Sony were PWM free.

And this year : W800C & W850c until now.

Now the people here http://www.rtings.com/ introduced a new testing methodology and reviewed all over again all 2015 TVS for motion blur (response time).

Also captured back-lights flickers !

http://www.rtings.com/latest-reviews

Press on a TV review -> go to Video Games -> click on the number for Response Time and see this http://www.rtings.com/images/reviews/w8 ... -large.jpg -> click the link near Backlight: picture and see this : http://www.rtings.com/images/reviews/w8 ... -large.jpg

In case of PWM use it will look like this on the blue line :

http://www.rtings.com/images/reviews/j6 ... -large.jpg

http://www.rtings.com/images/reviews/j6 ... -large.jpg

Now available for all models !
Enjoy !!!
By Mark Rose
#7370 I recently purchased the w700c and it is also PWM-free. It's not available in the US, so it's unlikely rtings will review it.