s25 Ultra - Severe Eye Strain - PWM Causing TLM

[FirebirdFormula]

Hello.  I recently swapped an s21 Ultra to an s25 Ultra.  I loved/love both phones, outside of the eye strain that the s25 Ultra is giving me.  Unfortunately I cannot use it for more than 2-3 minutes at a time without feeling the strain which then lingers for hours and interferes with sleep.  I have only ever experienced this with certain computer monitors, never with a mobile device.

The issue is referred to as temporal light modulation (which is often referenced as "flicker") theoretically caused by the use of pulse width modulation.  One can read about more users having this problem here.

This has created quite a headache (no pun) with the Verizon store as my s21 Ultra that I traded in is no longer available to me.  They're ordering me a new s21 Ultra and are going to be in touch this week.

I would really, really like to keep the s25 Ultra, outside of this, I love this phone and even with a trade-in, paid a premium for it as I did the s21 Ultra.  I am curious if there are any efforts or plans to address this or if anyone has any ideas.  I am a power user & all display options & developer options do not help.  

Thank you for your time.

[johnz237]

It sucks youre experiencing such discomfort, as someone who needs to take breaks from screens before strain. Have you tried turning on eye care in settings? Maybe consider getting a screen protector with a filter on it too

[Joeeye]

It's quite unusual to have this issue if you never experienced this with your S21. I am unsure as to why the S25 Ultra would be any worse than using the S21 Ultra.

[FirebirdFormula]

Thank you both for chiming in.  Color (red/blue) light doesn't help as it appears to me as a very fast flicker.  And yes, the s21 did not do this to me at all - the only time I've ever experienced this was with certain computer monitors.  I have a feeling I may be in a minority here with this sensitivity.

[Moiramon]

Have you tried changing the refresh rate. Just thinking that the adaptive refresh rate on the S25 can go from 1 to 120. The S21 goes from 60 to 120 refresh rate. You could try changing it to the 60 refresh rate.

[GoanGeek]

Hi.

Have you tried the qhd setting?

Don't see what could cause the issue.

[FirebirdFormula]

Hi, I have tried both locking the  refresh rate and QHD.  Now I'm experimenting with dimming apps mentioned here and here.

It's very difficult to troubleshoot because once the strain kicks in, it stays for hours unless you pretty much abstain from using the device.  I am going to borrow an s21 Ultra from a friend tomorrow and will go from there.  Thank you for your replies.

[JoeD24]

Given you didn't have issues with the S21 Ultra, I wouldn't suspect PWM as the cause. Per Notebookcheck, the S21 Ultra has a PWM range of 227 to 250 Hz. The S25 Ultra has a constant 480 Hz frequency. Higher = better for PWM sensitive users

One difference I can see is the adaptive refresh rate. The S25 will cycle between 1 and 120hz when set to Adaptive, and will still cycle between 1 and 60 when set to Standard. If you enable the refresh rate overlay in developer settings, you'll see the rapid cycling. I notice even at Standard, it's cycling back and forth rapidly in certain apps (e.g. Whatsapp). 

From what I could find online, the S21's adaptive refresh (which was included in an update) doesn't go as low as 1. That could be the key difference causing your headaches. 

[FirebirdFormula]

Hey JoeD24 - I have read extensively about this but your post got me thinking about it again - perhaps it's specifically the STEP rate the phone is capable of vs the actual cycling.  Ideally and theoretically, a step rate of 10 between 60-120 (but not to go below 60) may solve this problem vs. the 25's ability to step in increments of 1 from 0.

I'm going to experiment by freezing a few background apps which may influence this & finding a way to lock in specific refresh rate changes.  We may be onto something here - I will post back regardless.

[FirebirdFormula]

FYI, I realize I didn't address a few other things you'd mentioned.  10-4 on the refresh rate overlay - I actually turn on dev options within minutes of getting a phone and specifically turned on the overlay in the car on the ride home because maps was starting to give my eyes that "itchy" feeling.  edit - it's truly unique how strong the effect is.  Even if the phone is on a desk & only at the corner of my eye I can feel it (almost like it's radioactive lol).

Regarding PWM, I thought maybe the higher number was effecting me negatively - I know very little about the technology.  My guess is you're right on this one.

Very excited to test this, I plan on implementing it tonight and testing once my eyes have straightened out - right now they're about 90% better.  Need to be 100% to confirm this actually works, that the biggest pain in troubleshooting this!  Thank you again - will post back.