So you may have come across the 3 letters PWM among these various forums when people discuss the OLED iPhones and the rumour that the 12 series will all be OLED based.
Some of you wonder why some of us make a big deal of it because you can’t see it or it doesn’t effect you, well I have a video I recorded of my laptop which shows PWM in action in quite a dramatic fashion which hopefully might visually show why some of us are really worried about an all OLED iPhone lineup.
So what is PWM? PWM stands for Pulse Width Modulation and is used in various applications for reducing the brightness of lights or slowing down motors etc, it is a Pulse of electricity rather than a constant source of electricity and Pulsing lights at high frequencies has the effect of making them appear dimmer to the naked eye due to how our sight works. PWM is an all digital solution and cheaper/smaller to implement the controllers vs an analogue controller which would lower the voltage/current.
Some of us are sensitive to PWM in lighting applications and it can cause eye strain and headaches sometimes these can be quite severe. This is because when you dim a screen you are generally in a dim environment and your pupils are dilated to let in maximum light and the screen of the device you are using is pulsing at full brightness directly into your dilated pupils causing eye strain and headaches. Most people won’t suffer from this and those of us who do don’t realise it is happening because the pulsing is happening fast enough for us not to see the flicker with our naked eyes.
PWM itself is not actually the issue for most of us, what is the issue is the frequency of the PWM the lower the frequency the more pronounced the flicker and that is what causes the headaches. For me personally when PWM gets to around the 200hz mark that is when I get headaches, yet my TV which is a Sony Full Array local dimming set uses a PWM frequency of 720Hz which isn’t an issue for me unless I activate the black frame insertion mode which lowers the PWM to 120Hz.
So why is it a problem on iPhones then? Well iPhone OLED’s pulse at 240Hz which is where most of us will feel the eye strain. I had an iPhone X for a year and got these headaches that couldn’t be explained I went to the opticians the doctors etc but they couldn’t figure out why, it was only when I stumbled across a post on this forum where I realised that was the issue. When I traded my X for an XR the headaches went away.
Well the last couple of weeks the headaches came back, turns out the LCD in my cheap little ExBusiness laptop I recent got uses PWM at 220Hz a very similar frequency to the iPhone. As it was an LCD I never thought it would use a PWM frequency that low so it never occurred to me that it was causing my headaches until I recorded this video...
The Lenovo X230 with PWM is to the left and my 2012 MacBook Pro is to the right, see how dramatic the PWM is with the flicker and black strobing bar on the screen. This is the cause of our pain. I would love to know how this would effect people with epilepsy as if it’s enough to cause us eye strain and headaches god knows what someone with epilepsy would be going through.
PWM is needed in small OLED screens because you cannot simply lower the voltage to dim the screen as it causes the colour to shift and go all wonky, so this is why a lot of us are concerned about an all OLED iPhone lineup going forward because we will no longer have an upgrade path. What is also concerning is everything bar the cheapest Android phones or the iPhone SE (which for us with an iPhone XR or 11 would be a downgrade) all use an OLED screen. This is why you see PWM mentioned a lot in these forums.
Hopefully this video will show what you can’t see and hopefully it will show you why some of us really struggle with certain screens.
Some of you wonder why some of us make a big deal of it because you can’t see it or it doesn’t effect you, well I have a video I recorded of my laptop which shows PWM in action in quite a dramatic fashion which hopefully might visually show why some of us are really worried about an all OLED iPhone lineup.
So what is PWM? PWM stands for Pulse Width Modulation and is used in various applications for reducing the brightness of lights or slowing down motors etc, it is a Pulse of electricity rather than a constant source of electricity and Pulsing lights at high frequencies has the effect of making them appear dimmer to the naked eye due to how our sight works. PWM is an all digital solution and cheaper/smaller to implement the controllers vs an analogue controller which would lower the voltage/current.
Some of us are sensitive to PWM in lighting applications and it can cause eye strain and headaches sometimes these can be quite severe. This is because when you dim a screen you are generally in a dim environment and your pupils are dilated to let in maximum light and the screen of the device you are using is pulsing at full brightness directly into your dilated pupils causing eye strain and headaches. Most people won’t suffer from this and those of us who do don’t realise it is happening because the pulsing is happening fast enough for us not to see the flicker with our naked eyes.
PWM itself is not actually the issue for most of us, what is the issue is the frequency of the PWM the lower the frequency the more pronounced the flicker and that is what causes the headaches. For me personally when PWM gets to around the 200hz mark that is when I get headaches, yet my TV which is a Sony Full Array local dimming set uses a PWM frequency of 720Hz which isn’t an issue for me unless I activate the black frame insertion mode which lowers the PWM to 120Hz.
So why is it a problem on iPhones then? Well iPhone OLED’s pulse at 240Hz which is where most of us will feel the eye strain. I had an iPhone X for a year and got these headaches that couldn’t be explained I went to the opticians the doctors etc but they couldn’t figure out why, it was only when I stumbled across a post on this forum where I realised that was the issue. When I traded my X for an XR the headaches went away.
Well the last couple of weeks the headaches came back, turns out the LCD in my cheap little ExBusiness laptop I recent got uses PWM at 220Hz a very similar frequency to the iPhone. As it was an LCD I never thought it would use a PWM frequency that low so it never occurred to me that it was causing my headaches until I recorded this video...
The Lenovo X230 with PWM is to the left and my 2012 MacBook Pro is to the right, see how dramatic the PWM is with the flicker and black strobing bar on the screen. This is the cause of our pain. I would love to know how this would effect people with epilepsy as if it’s enough to cause us eye strain and headaches god knows what someone with epilepsy would be going through.
PWM is needed in small OLED screens because you cannot simply lower the voltage to dim the screen as it causes the colour to shift and go all wonky, so this is why a lot of us are concerned about an all OLED iPhone lineup going forward because we will no longer have an upgrade path. What is also concerning is everything bar the cheapest Android phones or the iPhone SE (which for us with an iPhone XR or 11 would be a downgrade) all use an OLED screen. This is why you see PWM mentioned a lot in these forums.
Hopefully this video will show what you can’t see and hopefully it will show you why some of us really struggle with certain screens.