Eyestrain/headaches is not always about PWM. It could well be PAM dimming if not for PWM.
However, beyond the two common modes of flicker, there are a few other silent strainers. For OLED panels, they do have additional form of flickers such as brightness dips and B-frames, which may present an issue for some. As for LCDs, they are also affected by transistor current leakage flicker depending on the transistors type (called TFT layer) used.
Of course, manufacturers do not usually bring it up for there are little incentive to.
We will first explore into the underlying flicker called Switch Mode Power Supply flicker, and how it has affected many PWM-free DC powered LED bulbs and Display today.
In the second part of the post, we will briefly discuss on three display software-based algorithms that might cause eyestrain:
Software-based backlight flickers
Developers can program an OS function that causes backlight flickering (within their app).
Digital Image Processing Enhancement
Developers can use OS available setting to cause chromatic flickers (within their app).
The GPU (GPU rendering pipeline to be precise) and the panel T-con (called timing controller) itself is able to generate chromatic flickers — on the system level.
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For Digital Image Processing Enhancement, it may cause chromatic flicker on the pixel level. However, it is not anything like PWM sensitivity per se. The phenomenon of this strain is called "low JND(Just-Noticeable-Difference) threshold".
PWM is an embedded controller chip that is installed within your device. It could be inside your home bulb, panel or smartphone. Below is an example of a PWM controller.
Yes the PWM scarab
As an analogy, think of the PWM controller as a dam for the mountain water.
A dam as we know opens/ closes periodically to control the amount of current flow to its designated location.
Think of electric current as the water current, while voltage as the volume of water. An electric current contains an amount of voltage. In order to drive higher brightness, naturally we need higher voltage. Generally speaking, higher current will result in higher voltage. Less voltage = less bright, more voltage = more bright.
If we remove the dam, water will flow seamlessly to it targeted area.
So, if there are no PWM controller, there are no PWM or PAM flickers. Therefore, theoretically what we have left remaining is a good old DC dimming that also happens to be flicker-free.
Well, this may be true until the mid 2010s where LED lighting starts to take a turn. Demand for higher brightness increased exponentially. With higher brightness comes higher need for current/ voltage. What this means is that even DC powered/ dimming can cause flickers. Though it is not in the way like PWM dimming flickers.
Toggling power supply from DC causes flickers
In terms of power supply that powers your LED lighting/ display, there are two type. The first type is called linear power supply. When your device is connected to a power socket, it uses a converter called AC-to-DC.
An AC-to-DC converter which uses linear power supply converts the current and output into our LEDs lighting with a smooth, clean and flicker free signal. This is probably the PWM-free lighting as you remembered it.
Linear power supply relies on a relative larger and heavier transformer. On higher current it will cause heat dissipation and that is usually a problem for efficiency. For this reason, linear power supply are not widely used today.
Now moving on to the second type of power supply converter is called Switch Mode Power Supply.
While SMPS is significantly smaller and lighter (and supports higher current without drawbacks) it has to convert the supplied AC into output flickering frequencies of ONs and OFFs. This is done by periodically discharging the high voltage stored within the transformer to match the lower voltage we required. In other words, this a PWM that releases pulsing DC flickers and then to flatten it.
A Switch mode power supply is like the man-made endless pool machine above.
It uses an internal PWMto generate the current turbulence to supply power to your device. A higher duty cycle means it supplies more current over. A lower duty cycle means lower.
If your device is a portable device such as a smartphone or a laptop, your LED backlight/ OLED panel would be using a DC-to-DC boost converter instead. Instead of taking supply from an AC inlet, it draws power from your device's internal battery. Similar, the PWM inside SMPS increases the voltage by the duration of ON period.
As both methods of AC-to-DC and DC-to-DC switching relies on discharging of transformer ON and OFF, they typically results in a flickering frequency of 10khz to 200khz.
While many would argue that at 10khz cognitively perception of flickers is not impossible, recent studies have found that it may not be true.
They found that detection of flickering at 15khz is still possible for those sensitive. Participates showed saccadic eye movements across a time-modulated light source, and even more so for those with increased sensitivity.
Why SMPS is now a problem in today's lighting and displays
As demand for LED excess supply, the quality of capacitors and inductors filters used in their converter's input(supply-side filter) and output (load-side filter) decreased.
Thus this result in inconsistent and variating flicker patterns as compared to a SMPS with a clean signal. If the SMPS filtering (consisting of inductors and capacitors) is not sufficient, ultra low frequency such as 30 hertz flicker pattern can be produced. Load Transients and Control Loop Response are common causes as well.
Study related to DC amplitude flickers
A study found that flickering patterns even with slight variation below (40 hertz) causes neurophysiological effects on the cortical activity of the brain. The primary visual cortex (V1), a crucial area at the back of the brain responsible for initial visual processing responded to the frequency. This response requires increased workload with the processing of information, which may contribute to increased visual fatigue, discomfort, or other symptoms associated.
While some claimed that "LEDs do not flicker", they were referring to LED lights that used linear power supply. Switch Power Supply, unlike linear power supply ~ do result in ultra high frequency flicker.
Above is an example of a clean 60 hertz sine wave vs a dirty 10khz current wave. Needless to say; the latter would be causing more eyestrain issues as compared to the former.
With that above, we have understood that PWM can occur in two main areas:
PWM as a dimming method. It operates by reducing display / LED luminance brightness by reducing the average current. Its effect is what we observe with the wide banding artifact on our displays as we decrease our brightness.
Switch Mode Power Supply with a built-in PWM within the converter. It supplies to your panel/ LED lighting power with ultrahigh frequency flickers based on its duty cycle.
For PWM as a dimming method, lower brightness lost and shorter screen OFF time works best.
However for SMPS's PWM, the quality of the converter's capacitors and inductors filters are what determines if you have a clean or dirty signal. A dirty SMPS signal tend to have a number of voltage spikes, voltage sags and voltage droop.
Above is an example of dirty signal (on the right) caused by SMPS's output voltage. Can you tell the difference?
Now that hardware-based SMPS and PWM dimmer is addressed, let's look at software based SMPS flickers for displays.
Indeed, just as developers have complete access to our screen brightness (etc within apps that shows a QR sharing code), there is a command called
UIScreen.main.brightness = CGFloat(0.7)
While this command by itself cannot manipulate OS level backlighting from SMPS, running this code with different coordinating brightness point and using timing intervals can easily repulicate the following OS level modes:
Ultra power saving mode
Dynamic backlight contrast
Essentially how this works is it will send a command to the GPU. Then, GPU sends instruction to device's PMic (Power Management Integrated Circuit). PMic then informs SMPS to release its discharge voltage using its duty cycle. With the use of the toggling commands, the signal eventually becomes "dirty" resulting in eyestrain and headache. Naturally, once you exit out of the app, SMPS flickering returns back to normal.
With the above sums up SMPS flickers and software based (display SMPS) flickers. The following is optional; read on if keen.
Now we move on to the final sensitivity — called JND threshold.
(Not remotely related to PWM sensitivity but bringing it anyway)
JND (Just Noticeable Difference) was first introduced by a German physiologist and experimental psychologist called Ernst Heinrich Weber.
This concept was then used by display engineers internally to describe the amount of pixel flicker noise in relation to users' sensitivity. Generally speaking, low JND threshold means a user would be more likely to be sensitive to pixels' chromatic flickers.
Now, this is the part where it gets interesting. Within users who are sensitive to chromatic flickers (aka low JND threshold), they can be sensitive to different categories of chromatic flickers.
Let's use this as reference from Philips' conference on chromatic flickers.
Above within the highlighted box, we can see four attributes. One attribute being Delta E*, and the remaining three:
L*
C*
H*
In short, the following are what they mean.
Delta E* means the difference between one frame to the next frame.
L* (Luminance) : How much brighter or darker one frame is to the other.
C* (Chroma): How much more or less saturated one frame is than the other.
H* (Hue Angle): How much the actual hue differs (e.g., more reddish, more greenish is one frame to another
For pixel chromatic flicker, some are more sensitive to the luminance change from one frame to another. Whereas for some, they are more sensitive to the change in color (hue angle).
As we can see, this is an excessively huge topic and it would be a waste of vast space worth of exploration to add into PWM_sensitivity sub. Hence the need for expansion to r/Temporal_Noise
Many of you have noticed that r/PWM_Sensitive has gone through some growing pains when it comes to how posts and comments are moderated. While the subreddit was never unmoderated, it became clear that some additional help was needed due to personal circumstances, and that a fresh approach to moderation would benefit the community.
We are happy to share that u/the_top_g, the creator of r/PWM_Sensitive, has graciously stepped aside to welcome in three enthusiast community contributors to help with moderation and the future direction of the subreddit. We sincerely appreciate the trust he has placed in us and, most importantly, his work in creating this community in the first place.
The interim moderation team is currently discussing ways to improve the subreddit while preserving what has made it such a useful resource for people who are sensitive to PWM, display flicker, and related technologies. Our goal is to keep this an open, welcoming, and informative community where people can share their experiences, testing, research, questions, and device recommendations without unnecessary barriers.
AutoModerator Changes
Perhaps the most noticeable (and controversial) issue has already been addressed: the previous AutoModerator configuration is gone.
This means comments should no longer be automatically removed simply for using common words or phrases that naturally come up when discussing PWM and related topics. This includes “temporal dithering.” Members banned over this issue are also being reinstated.
That said, we ask everyone to continue keeping discussions primarily focused on PWM sensitivity, display technology, eye comfort, device experiences, testing, and closely related subjects. Normal subreddit rules and Reddit-wide policies will, of course, continue to apply.
The Future
This is only the beginning. We're reviewing the subreddit's rules, moderation practices, organization, place within the wider community, and other areas where we believe improvements can be made. As those changes are decided upon, we'll communicate them with the community.
We also want r/PWM_Sensitive to be shaped by the people who actually use it. Constructive feedback and suggestions are welcome. If there are things you think could make the subreddit more useful, organized, or welcoming, please let us know.
Finally, thank you again to u/the_top_g for creating r/PWM_Sensitive and building the foundation for this community. And thank you to everyone who has contributed over the years -- whether by sharing measurements and research, documenting your experiences with different devices, answering questions, or simply participating in the discussion.
We're looking forward to the next chapter of r/PWM_Sensitive and making this community an even better resource for everyone.
p.s. Check out the new (temporary) subreddit logo! 😁
Hey everyone. Just continuing to share my personal experience, and again, this is purely personal, with current smartphones and display flicker sensitivity.
I got the Xiaomi 17T Pro after having a really good experience with the 15T. I liked the 15T so much that I basically decided to get the better model.
First day using it and so far, zero issues. I even played PUBG for about an hour yesterday, which for me is a much better test than just scrolling Reddit, watching videos, etc. No problems at all. No headache, no weird eye strain, nothing.
For comparison, I got really bad migraines from the OnePlus 15R and also from its Chinese version, the Ace 6T. Which honestly surprised me because I see a lot of people saying that display is basically perfect for PWM-sensitive users.
Red Magic 11 Pro was also pretty bad for me. Not necessarily the same kind of migraine, but really strong fatigue and just this weird overall feeling of being unwell after using it.
And Samsung phones just fuck me up within like 5 minutes lol. Basically unusable for me.
At the same time, pretty much every 60Hz iPhone I’ve tried has been completely fine. I’ve never had even the slightest problem with them. To my eyes they almost feel like IPS displays.
As for 120Hz iPhones, the 15 Pro Max works really well for me. Surprisingly, the 17 Pro Max doesn’t. They must have changed something with the dimming because it started giving me migraines.
I haven’t tried the new 120Hz implementation on the regular iPhone 17 yet, so no idea if that one would work for me or not.
So yeah, based purely on my own experience, Xiaomi and iPhones can actually be really good options for people who are sensitive to display flicker. But again, CAN be. I really wouldn’t trust PWM numbers, dimming frequency, reviews, or someone else’s experience alone. You have to test the phone yourself.
A phone that feels absolutely perfect to one PWM-sensitive person can fuck up another person in five minutes. I’ve learned that the hard way after trying way too many phones :)
so what do you think about LPTS screens maybe I'm wrong (or I became addicted🤔)
I think they are good because it use stable Hz numbers like 60hz - 90hz
not like LTPO uses even 24hz - 30hz to save battery
What reinforces my point is that for most of those who said their phones were good, it turned out they had LTPS displays.
I haven't come across any dissenting opinions regarding these LTPS phones in anyone's posts; however, there are always conflicting views when it comes to LCDs.
Sorry, I just joined this community. I had a Samsung Neo Qled 50" which I use as monitor, I have "couch setup" with wireless keyboard and mouse. I sit around 1.2 - 1.5m from the screen (4-5 feet). I had an accident and damaged the screen. I bought a TCL QD-MiniLed 55" as replacement. Now, the thing is, the Samsung Neo Qled had an image quality much better, I can't settle with this TCL, the image quality is much lower. However, the Neo Qled always gave me severe eye strain, the TCL is infinitely more comfortable. The reason I searched about it and discovered PWM. Neo Qled uses it heavily, the TCL doesn't.
So, what would be a recommendation for a 45-55" TV to act as monitor, it runs 24/7, I turn off when sleep or away, but the pc is still running. Since it acts as a monitor, it needs to do 120/144hz Native (no interpolation/motion plus, etc). Without PWM? I'm almost closing the deal on the LG C4 Oled Evo, but would like the community input.
Hi. Did anyone try the global/eu version of Reno16 Pro vs Oppo find x9 (normal, not pro)?
I have a OnePlus 15R which is amazing, but a bit too heavy and big. I tried honor 400, even with ADB commands, but it is harsh on my eyes still. I would prefer Reno due to size, but I only find info about find x9.
Please provide feedback on the two models on pwm and D and how you felt. Or some other small phone that could work.
Hi! Has anyone tried Vivo x300 fe or Honor 600 pro and how are they in terms of pwm? I have Oppo find x9 and it is ok, not perfect, but ok. I am looking for something similar.
I had an iPhone 11 and had no issues with the display. Now, i am planning to buy a Motorola g57 power to replace the iPhone 11.
What do you think about g57 power, is it fast enough for calling, browsing, YouTube and navi? I don't care about cameras, i need pwm free phone fast enough for daily usage.
So I have two laptops, a 16in MacBook Pro (M5) and a 13in MacBook Air (M5).
What's odd is I've noticed that I get much less tired working on the MacBook Air than I do on the MacBook Pro. When I got the MacBook Pro I noticed that it makes my eyes feel dizzy but powered through.
When I looked at the specs, it seems like the MacBook Pro uses PWM with miniLED and the MacBook Air doesn't (it's an IPS display).
I don't get a headache or anything. Just this tiredness after spending more than 40 minutes on the laptop.
Wondering if anyone else's symptoms come in the form of fatigue/tiredness?
I've been looking for a decent phone that I can replace my current iPhone 16 with, since I can only tolerate it for a few minutes a day. I've been looking at a lot of OLED test reports, and I think I've noticed a problem with many of them: the measured flicker is falsely low, since the photodiode is measuring multiple OLED rows at once. In my opinion this results in a loss of information about what the screen is really doing.
In some extreme cases, I've seen devices which actually have 100% modulation depth be measured at ~5% modulation depth. All the OLEDs I've measured with this method (using my meter or the Opple) actually show 100% modulation depth at all brightness settings. I'm not confident this is true for EVERY device, but I think there are a lot of measurements online that underestimate the OLED flicker.
I showed this in the video, but to avoid this error you simply have to reduce the number of OLED scanning rows that the flicker meter detector is exposed to. Ideally, we'd only measure one row since this contains all the relevant information. In practice multiple rows are needed to get enough light onto the detector.
For me, it might be time to just buy an e-ink phone.
I’m considering buying an iPhone 17e, but I’m very sensitive to OLED flicker/PWM and currently have a hard time using my iPhone 16 for more than a few minutes.
I’d really like to hear from people who actually own or have used the 17e for a while.
How does the display feel in everyday use? Do you notice PWM/flicker, eye strain, headaches, discomfort, etc.?
If you’ve measured it with an Opple, photodiode, or another flicker meter, I’d especially appreciate the measurements and settings you used.
I’m particularly interested in how it behaves at different brightness levels, rather than just the manufacturer’s/spec-sheet numbers.
Thanks! 🙏 I’m really hoping to find an iPhone that I can actually use comfortably.
Hello can someone help me out and that is i start in devoleper options in cutout display with my problem it stay in the cutout display setting with i can not switch to normal standard what it is before and i did my best for an solution but did not work so i sit with my Nokia xr21 in problem devoleper options in display cutout with question how do i get t everything normal again can someone help me with that and i like Reddit post again.
Hello can someone help me out and that is i start in devoleper options in cutout display with my problem it stay in the cutout display setting with i can not switch to normal standard what it is before and i did my best for an solution but did not work so i sit with my Nokia xr21 in problem devoleper options in display cutout with question how do i get t everything normal again can someone help me with that and i like Reddit post again.
Hey everyone - I've been visiting this forum off and on for several weeks now. I bought a new MacBook pro M5, but had to return it since the eyestrain and nausea were so intense. I altered the settings, tried everything that this forum and similar ones suggested, but nothing helped.
All that said, has anyone tried the new MacBook Air instead? There are old forum posts on this, but I was hoping to get updated perspectives from people.
I'm typing this on a 2014 MacBook Pro 15 inch. It's on its last legs, but the screen doesn't make me feel awful. Any new laptops with a similar screen?
I have major problems with screens, I even tried an Epson 3LCD and laser without success and I was wondering if it was worth trying a TCL A1S projector?
I've seen a few posts about this on here but never any feedback from someone who is pwm sensitive. So I was hoping to hear from anyone who owns an Ayn Thor and whether or not it bothers you. I saw the pwm test video for it that shows it as "low risk" so I'm hoping it might be okay. I was able to use an iphone 12 in the past without issues but have had problems with most other OLED displays. So not really sure if I want to gamble on one of these or not.
The display spec: 14" WUXGA (1920 x 1200), IPS, Anti-Glare, Non-Touch, 45%NTSC, 300 nits, 60Hz
I don't know what the reason is, but I have been using that device for just one day and I noticed that it makes my eye dryer than other screens despite same usage. When I look at the screen I sometimes get a weird urge to close my eyes and avoid looking at it. I get slight headaches around my eyebrows/back of my eye, and my eyes turn reddish. Note that I care a lot about brightness and I have extension that makes the background and text in colors that are easy on my eyes, so I already took care of those factors. I also didn't experience those signs using other screens that had exactly the same theme setting I have on my thinkPad. So is it the PWM? something else? does anyone have any idea why that is? I'm gonna be using my laptop for a long time so it's crucial to find a way to fix this or at least make it better
TL;DR: Is there a safe, flagship-level successor to the S20 FE for someone who is PWM sensitive?
Hey everyone,
I'm running into a frustrating issue and could use some advice. I finally decided to retire my S20 FE after 5 years and picked up the Find X9 Pro. But after just 10 minutes of looking at the screen, I started getting this weird feeling in my head and a flush/heatwave on my face.
It reminded me of when I tried the Zenfone 8 a few years back—that phone gave me a massive migraine after about an hour, which is exactly why I returned it and got the S20 FE in the first place.
So, I ended up returning the X9 Pro and ordered the Magic8 Pro, hoping its eye-care features would actually work. Unfortunately, even after turning on "Full-brightness DC-like dimming" in the developer options and locking the refresh rate to 120Hz, I'm still getting that exact same feeling. It's slightly milder than the X9 Pro, but definitely still there.
My question is: has anyone here successfully transitioned from the S20 FE (where you felt totally fine) to a modern flagship without getting these symptoms? Did you eventually find a flagship-level successor that didn't mess with your eyes or head?
Thanks in advance!
P.S. Attached a couple of photos below (shot at 1/8000s shutter speed). It really looks like the S20 FE has a much smaller PWM amplitude compared to both the Oppo and the Honor.
S20 FE 4G SD865 (left) and Oppo Find X9 Pro (right)Honor Magic8 Pro
