PWM

jtl999 · Aug 3, 2016 at 6:30 AM

Seems the Galaxy Note7 uses PWM

It's a shame, because my (and some other peoples) eyes are too damaged to handle screens that have PWM (nearly all)

I wish Samsung would really do something about this once and for all, maybe have a hidden option to disabled PWM that is activated with those dialer codes, etc.

https://www.youtube.com/watch?time_continue=131&v=SzCgp-FEU50 (skip to 2:10)

http://i3.mirror.co.uk/incoming/art...s615b/Samsung-Galaxy-Note-7-Weibo-leaks-1.jpg

Diaconescu_Tiberiu · Aug 3, 2016 at 8:43 PM

what is PWM... excuse my ignorance

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Devhux · Aug 4, 2016

Diaconescu_Tiberiu said:
what is PWM... excuse my ignorance

Sent from my SM-N910F using Tapatalk

I think it stands for Pulse Width Modulation.... Basically it causes the displays to have a slight flicker to them at lower brightness settings as the display is switched on and off very rapidly.

Pretty sure PWM isn't something that can be turned on or off via software - it's how the display controller manages brightness levels.

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Diaconescu_Tiberiu · Aug 4, 2016 at 12:24 PM

It can be controlled (diminishing its effects) via Lux Dash app

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Ace&tripleD · Aug 4, 2016 7 0 0

Diaconescu_Tiberiu said:
It can be controlled (diminishing its effects) via Lux Dash app

Sent from my SM-N910F using Tapatalk

Thanks Tiberiu,
I'm also interested in a solution to pwm, how can this app mitigate the effect of the flickering ?

millab · Aug 5, 2016

Unfortunately Pwm cannot be 'turned off' except possibly by having the display at full brightness all the time. Any reduction in brightness uses PWM.

Every LED screen and light is dimmed by PWM in any product on the market. The difference some people see (myself included) is the frequency used for PWM, and that is dictated by hardware or very low-level software in the display controller.

jtl999 · Aug 5, 2016 at 1:44 AM

millab said:
Unfortunately Pwm cannot be 'turned off' except possibly by having the display at full brightness all the time. Any reduction in brightness uses PWM.

Every LED screen and light is dimmed by PWM in any product on the market. The difference some people see (myself included) is the frequency used for PWM, and that is dictated by hardware or very low-level software in the display controller.

Not 100% true. BenQ monitors and Macbook's (above 50% brightness) don't use PWM for example

Even then on the Macbook example it's still over 100Khz according to some contacts of mine.

jtl999 · Sep 7, 2012 143 22 0

Ace&tripleD said:
Thanks Tiberiu,
I'm also interested in a solution to pwm, how can this app mitigate the effect of the flickering ?

By leaving the actual hardware screen at full brightness and using an overlay to "dim" the image. Unfortunately this still has battery life implications and some phone screens still use PWM at full brightness, it's much less apparent but can still hurt me.

Ace&tripleD · Aug 4, 2016 7 0 0

jtl999 said:
By leaving the actual hardware screen at full brightness and using an overlay to "dim" the image. Unfortunately this still has battery life implications and some phone screens still use PWM at full brightness, it's much less apparent but can still hurt me.

I know this is working on an ordinary LCD screen, but will it work on a OLED one too ?

jtl999 · Sep 7, 2012 143 22 0

Ace&tripleD said:
I know this is working on an ordinary LCD screen, but will it work on a OLED one too ?

In what way?

Ace&tripleD · Aug 4, 2016 7 0 0

jtl999 said:
In what way?

well the technology is different: on a LCD dimming by using a darker overlay will only affect the liquid crystal keeping the backlit at full power, but on a OLED not sure how it works at the pixel level - probably the only way a pixel gets darker is by starting to flicker. In this case a dimming overlay will still produce pwm...

jtl999 · Aug 14, 2016

Ace&tripleD said:
well the technology is different: on a LCD dimming by using a darker overlay will only affect the liquid crystal keeping the backlit at full power, but on a OLED not sure how it works at the pixel level - probably the only way a pixel gets darker is by starting to flicker. In this case a dimming overlay will still produce pwm...

Your exactly right, and I believe it is implementation dependent and may have seen it in youtube videos captured at the right shutter speed. But it doesn't happen that way on all phones.

Also my cousin showed me his Moto X (AT&T version) and it appeared to be AMOLED but PWM free at any brightness. Anyone help me out and find what version it is?

I just messaged him and will edit if he gets back to me.

It was either a first or second gen Moto X that was AMOLED but didn't use PWM. A potential reverse engineering target? In any case I might be seeing him in Mid September so I would check again.

millab · Aug 24, 2016 at 4:04 AM

jtl999 said:
Your exactly right, and I believe it is implementation dependent and may have seen it in youtube videos captured at the right shutter speed. But it doesn't happen that way on all phones.

Also my cousin showed me his Moto X (AT&T version) and it appeared to be AMOLED but PWM free at any brightness. Anyone help me out and find what version it is?

I just messaged him and will edit if he gets back to me.

It was either a first or second gen Moto X that was AMOLED but didn't use PWM. A potential reverse engineering target? In any case I might be seeing him in Mid September so I would check again.

I don't think you understand... Just because you can't see the PWM effect doesn't mean that it isn't using PWM - it just means the frequency is high enough that your eye can't see the flicker. It comes down to the frequency the engineers choose to use

californiarailroader · Aug 24, 2016 at 9:28 AM

I don't notice any flicker on my Verizon Note 7.

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Ace&tripleD · Aug 24, 2016

californiarailroader said:
I don't notice any flicker on my Verizon Note 7.

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congrats on ur note 7

could you lower the brightness to less then 50% and do the pencil test ? and see if you can spot this type of pattern ?

Nitemare3219 · Aug 24, 2016 at 5:27 PM

No need for that. Look at any review of the Note where the screen brightness is lower, or a picture of the screen. You will see the "scrolling lines" effect which is a result of PWM frequency and shutter speed of the camera not matching up.

LinS123 · Aug 24, 2016 at 5:35 PM

PWM is annoying at lower frequencies. It seems the Note 7 panel uses a high enough frequency where I can't see it flickering.

I know it varies from person to person but that's luck of the draw I guess. Some people will have no issues while others will get headaches.

Ace&tripleD · Aug 4, 2016 7 0 0

LinS123 said:
PWM is annoying at lower frequencies. It seems the Note 7 panel uses a high enough frequency where I can't see it flickering.

I know it varies from person to person but that's luck of the draw I guess. Some people will have no issues while others will get headaches.

hi, did you try the pencil test at low brightness ? I haven't found yet a review that measures the pwm more precisely

LinS123 · Aug 24, 2016 at 11:05 PM

I don't see any difference in the image at 0% and 25%. Not sure what I'm looking for. But no flickering for my eyes.

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Ace&tripleD · Aug 4, 2016 7 0 0

LinS123 said:
I don't see any difference in the image at 0% and 25%. Not sure what I'm looking for. But no flickering for my eyes.

Sent from my SM-N930W8 using XDA-Developers mobile app

just have a look at this video https://www.youtube.com/watch?v=QriSp-Ffgkg
there is definitely a stroboscopic effect on the pencil when moving it quickly

PWM

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