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Batman

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#251473 26-Jun-2019 22:19
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I just realised that a laptop I bought has a PWM screen, at every level of brightness.

 

Is that harmful as suggested by the interweb?





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michaelmurfy
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  #2265398 26-Jun-2019 22:26
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No. PWM is all around you.





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gehenna
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  #2265408 26-Jun-2019 22:35
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Wth is pwm?

michaelmurfy
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  #2265409 26-Jun-2019 22:37
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gehenna: Wth is pwm?

 

https://en.wikipedia.org/wiki/Pulse-width_modulation

 

Basically turning something off and on very fast. Used in LED lights, screens, TV's, computers, phones, speakers etc... It is how many devices operate.





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richms
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  #2265417 26-Jun-2019 23:00
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michaelmurfy:

 

No. PWM is all around you.

 

 

I sure dont like looking at screens with it. Hard to find a TV without it now since they all try to save energy to keep europe happy and panasonic even brag about having backlight flicker - or "blank frame insertion" as some marketing type called it.





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  #2265577 27-Jun-2019 09:22
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anyone else has any ideas? thanks





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  #2265625 27-Jun-2019 09:35
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Blank frame insertion is something different, that particular feature is to remove image persistence/blur or colloquially “ghosting” on lcd/led screens. Key difference is the intentional black image frame. It’s actually quite good on high refresh monitors (its called ULMB, Ultra-low motion blur).

Pwm is where the backlight, not the image, is modulated to reduce power while producing the same effect. Problem is if it’s not done right/ fast enough the human eye keeps up by contract/expanding the pupil causing eye strain/headaches/nausea.

Some people notice or get sick from it, others dont. To combat it buy monitors with no pwm or flicker-free features, OR turn your brightness all the way up and reduce image brightness/contrast through GPU drivers.

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  #2265633 27-Jun-2019 09:48
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Batman:

anyone else has any ideas? thanks



So to answer the question of whether it’s harmful, only if you react to it over a period of using it.

Use your laptop for a few hours or so straight. If you notice your eyes going red, dry/itchy or are blinking a fair bit then its fair to say you dont take to the particular implementation of pwm on that laptop.

It won’t do permanent damage straight away but once you know that you do react to it then stop using it and hook it up to an external monitor without the issue.



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  #2266521 28-Jun-2019 19:56
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So, I have become obsessed and testing everything for PWM

 

So it turns out Iphone OLEDs all have PWM at 240Hz, so does my Samsung Galaxy S10 Plus at 240Hz. My laptop is at around 200Hz.

 

My lights have flicker too, but I'm guessing that's at 50Hz?

 

Luckily none of my other laptops and monitor screens and OLED TV and LCD TV have PWM.

 

Not sure what to make of it really.





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  #2266524 28-Jun-2019 20:08
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Batman:

 

Luckily none of my other laptops and monitor screens and OLED TV and LCD TV have PWM.

 

 

I bet you they do... 





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gzt

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  #2266525 28-Jun-2019 20:18
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SpartanVXL: Pwm is where the backlight, not the image, is modulated to reduce power while producing the same effect.

Do the laptops switch that feature auto off when plugged in?

Batman

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  #2266534 28-Jun-2019 20:52
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michaelmurfy:

Batman:


Luckily none of my other laptops and monitor screens and OLED TV and LCD TV have PWM.



I bet you they do... 



Undetectable




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chevrolux
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  #2266550 28-Jun-2019 21:24
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Wait... is this thread real?

 

I don't care who you are... there is no way you can see flicker at 200+ Hz.....


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  #2266559 28-Jun-2019 22:15
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Quite obvious when you are reading white text on a black background which it has dimmed the backlight inorder to save a handful of watts. Instead of seeing solid text as your eyes move its a series of images. Not as annoying as going to the cinema but still bad.





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  #2266561 28-Jun-2019 22:27
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chevrolux:

 

Wait... is this thread real?

 

I don't care who you are... there is no way you can see flicker at 200+ Hz.....

 

 

you can't see the flicker.

 

but your eyes are reacting to them 200x per second and some people think that could cause damage





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