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
I wanted to share my 4-month experiment testing 7 different devices to find a setup that actually respects eye health and brain comfort. Using a display that hurts your eyes—even for just 5 minutes—can ruin your entire day. The eye strain, burning sensation, and brain fog don't go away the moment you put the phone down; your brain needs hours (sometimes days) to recover.
The Devices I Tested
Over the past 4 months, I cycled through:
Samsung Galaxy S26
iPhone 13 Pro Max
Tecno Camon 20S Pro 5G
Redmi 15
Huawei Y9s
Infinix Note 30 (Running Custom ROM: Evolution X)
The Journey & The Unseen "Enemies"
The PWM Nightmare (Samsung & iPhone): OLED displays on the Samsung S26 and iPhone 13 Pro Max were by far the worst. They caused burning eyes, tearing, and a distinct brain fog feeling (literally felt like my brain was a walnut rattling inside my skull for a day and a half).
Escaping to LCD (Huawei Y9s): Like many here, I fled to an older LCD device hoping for salvation. While it was better, my eyes were still straining. That’s when I realized the second enemy: 60Hz refresh rate. (Unfortunately, most laptops still run on 60Hz as well).
The Refresh Rate Switching Trap (Infinix, Techno, Redmi): Moving to 90Hz/120Hz LCD/AMOLED phones helped, but I was still getting subtle headaches. I realized there was a hidden, aggressive villain: Dynamic Refresh Rate Switching. Companies secretly drop your refresh rate from 120Hz/90Hz down to 60Hz the moment the screen becomes static—all under the guise of "battery saving." That constant, imperceptible jump between frequencies strains the eye muscles terribly. Trying to force a constant rate via standard ADB commands didn't work, as Android silently overrode my settings.
The Science & The Golden Rules
Comfort isn't tied to a specific brand; it’s tied to display technology and consistency. Here is what I learned:
LCD is still king for zero PWM, but it MUST be combined with high, steady refresh rates (at least 90Hz).
If using AMOLED: Look for PWM dimming frequencies above 1940Hz, combined strictly with LTPO panels. (Avoid LTPS panels as their transition between 60Hz and high refresh rates is slow, jarring, and hurtful to the eyes. LTPO switches much faster and smoother).
LOCKED Refresh Rate is Non-Negotiable: Your display must stay at a single frequency 100% of the time, regardless of interaction or battery level.
The Final "Recipe" & Salvation
I finally solved the puzzle by installing a Custom ROM (Evolution X) on the Infinix Note 30 (which has a 120Hz LCD display).
Why this combination worked:
Forced 90Hz Everywhere: Evolution X allowed me to hard-lock the screen to a strict 90Hz minimum and 90Hz maximum across all states (even on low battery).
The Battery Myth Busted: The battery drain from forcing a constant 90Hz is negligible. It is absurd that manufacturers silently drop refresh rates to 60Hz behind the user's back just to save a tiny fraction of power.
Bonus Perks: Beyond curing my eye strain, the custom ROM fixed Infinix’s notorious delayed notifications, provided ultra-smooth UI performance, added lock-screen charging wattage (like Samsung), and retained both fast charging and full camera resolution.
Takeaway
Don't just look at PWM frequency—watch out for micro-stuttering caused by dynamic refresh rate switching! Locking a good LCD panel to a fixed 90Hz brought my eyes and brain back to peace.
Hope this helps anyone struggling out there! Happy to answer any questions about the setup
Greetings to you all from Iraq! 🇮🇶 Stay safe and keep your eyes healthy.
Recently, many phones like the realme p4x, oneplus nord ce6 lite, moto g67 power and the vivo t5x have appeared and are really good options. However, they are india only and the only way to get them is by importing from india, which is not only sketchy (depending on the seller) and expensive, but risk that the phone doesn't work (even if the listing says that it's factory unlocked). How can we pressure these brands to release these phones to the global market? There are also the china only phones too like the moto g100 and redmi note 12t pro.
In your opinion, would you recommend a monitor? Is it true that it doesn't flicker and doesn't have blue light or reflections? I want to know the cheapest good type.
I suffer from LED/OLED-induced migraines, which probably have a PWM component. I've been getting by on a Samsung S10 - I can use it for brief things like checking an email/text or taking a photo, but can't use it for more than say 5 minutes at a time. I only use it for calls, texts, and photos. I have a work phone which is an iPhone SE and I tolerate it slightly better - but I hate the mac system.
My carrier isn't supporting 3G phones anymore, so I bought an S25. Setting it up induced a 3-day migraine. I get pain as soon as I use it for anything. The thought of reading a short email on it makes me cringe. I've (subsequently) read many similar user reports. I'm returning the phone, but now looking for an alternative. I've also tried to do a bit of skimming through the posts here and see that the OnePlus 15 is highly regarded. I've also seen praise for a few Chinese phones but am pretty leery about that. I'm interested in the SmartInk options, but taking good photos is one of my primary joys in a phone so I don't think they're a good fit.
Any recs? Ideally something someone in Canada could test drive at a store given the S25 experience (online purchase).
What is the reason for eye damage from the Poco C85 screen despite its high resolution TUV I activated the eye protection shield, adjusted the colors from saturated to natural, reduced the brightness, and refreshed the display, but it's still not working.
I know it has a terribly slow chipset, but I don't care much about this, my wife has the poco C75 with the same CPU and it is acceptable for basic use. So I am asking about the LCD display... GSMarena says it is flicker free but I had read bad things in this subreddit about other Moto phones with LCD displays.
I know a lot of people on here like iPhone 11 so I wanted to share one I have for sale. It’s 128gb with new battery and screen. I think an apple screen was used because it still has true tone. Battery health is 100%
Tried the iPhone 11 (horrible blurriness due to high response time latency when scrolling app), iphone 16 Pro (horrible dry eyes, headache, fatigue), iphone 17 (same as 16 pro), Pixel 10 (similar to the 11 because this OLED panel weirdly has a high response time - which is horrendous when scrolling apps), Poco M8 Pro (horrible dry eyes, fatigue, despite the marketing high PWM claims - notebookcheck says it is really only 120hz PWM).
So I am trying to find a suitable phone. But I don't trust any of the manufacturers. I am tempted by the Samsung S25/S26 because thier PWM is 480hz - and theirs works differently from the 480hz in some of the iPhones, but worried I will experience similar problems.
Has anyone had a similar experience to me and found something that works for them?
I purchased a “like new” refurbished iPhone 11 off Rebeelo. Luckily enough, I got the “sharp panel”. It has been updated IOS 26.2, I’ve disabled automatic updates.
However, I’m finding the display to look quite fuzzy / blurred. Text looks fuzzy.
I’m wondering if that’s normal for iPhone 11 display or if there may be an undetected screen replacement. I read if it is a random screen replacement and not Apple it can affect the sharp panel?
I’ve checked the parts / history. Nothing comes up. I know it’s definitely had a battery replacement, but that doesn’t come up in parts history either. True Tone also works.
i'd like to highlight my experience regarding my eye disease: Keratoconus
Is a rare degenerative disease that, over time (if it progresses), causes the eye to deform and take on a cone shape—irregularly refracting whatever the eye looks at (light, colors, etc.)—and makes the eyes extremely sensitive, to the point of causing severe headaches.
"Over 23.7 million individuals globally are affected by KC" (0.24%) (source) but maybe more that as to identify it requires a corneal topography: if you are very eye sensitive i'd like to suggest to do check your eyes with a ophthalmologist and if needed do a corneal topography to check if you're affected.
Having said that coming to the devices' screen: i cannot use any OLED, Mini-Led and some IPS as well. Based on my tests and investigations with screen technologies / specs, to avoid eye strain (Asthenopia) and headaches i'd like to suggest:
Avoid screens using PWM/PAM (any frequency) and D*ithering/F*RC
Avoid all OLED/QOLED etc and Mini led screens (OLED infinite contrast and Mini-Led Local dimming are a pain for the eyes)
Screens with >700 nits brightness (even IPS)
Screens oversaturated (avoid Adobe RGB color space, but I can somehow tolerate DCI-P3 color space coverage, even though using it for extended periods gives me a headache). (Oled cover adobe rgb and some mini led)
Always disable VRR (Variable Refresh Rate) or Apple's True motion and use static refresh rate
If you can avoid glossy (for TVs and laptops) and prefer matte screens as the reflections can be an issue. For smartphones is ok as usually have a decent (not good but fine) anti-glare coating.
i'm sure if you find something without the above mentioned specs you'll be fine 100%
i'm still using an iphone SE 2022 and will use it for long time (IPS, 100% sRGB, 8 bit native depth, 60Hz, no PWM, 600 nits max).
Last but not least, to carefully choose a device before purchasing:
For Laptops/Tablet/Smartphone chec Notebookcheck reviews before choosing one
I want your opinion on this phone and pwm tests (if it's pwm) if possible. Looks like the perfect phone for the moment being, I'm seriously considering getting this phone, however it's india only, so I'm considering getting it from ebay. Thanks!
Yesterday I got the Android 16 update on my TCL 50 Pro, and the phone became unusable for me, just like the TCL 60 Ultra and TCL 70 Pro - blurry text and somehow oversaturated whites. Activating bold text helped a little, but the phone looks bad with it enabled.
There is also no safe way to go back to Android 15 :(
I have an extreme reaction to some screens that effects my sleep and I’m trying to work out what is the specific cause so I can work around it. PWM seemed like and obvious cause from what I’ve read but my symptoms seem different to what everyone is reporting here. I don’t get the headaches that seem to be the symptoms for most.
The issue for me is if I use a screen after say 7pm or (as I discovered with a new monitor recently) even just using from 8am to 5pm for work - I either won’t be able to get to sleep or will wake shortly after falling asleep and not be able to get back to sleep. This is often quite extreme - the case with the new monitor stopped me sleeping all night.
Some screens are clearly better than others for me but nothing is safe enough for me to use after about 7pm. I’m loathed to test things for obvious reasons as if it’s positive it means potentially no sleep and a while to recover.
My only workaround so far is avoidance but often not practical today. Would be great to get any insight, advice or even if the consensus is that this is or is not PWM sensitivity.
Hi everyone! I’ve been posting here more often recently because my problems with phone screen flicker came back.
At one point, I switched from an iPhone 15 Pro Max to an iPhone 17 Pro Max, and that was when my symptoms started again. After that, it seemed like absolutely every OLED screen caused a reaction, no matter which phone I tried.
For example, I tested the OnePlus 15R, which is supposed to have one of the more comfortable OLED displays currently available, but I still experienced symptoms. I had severe headaches, pain and discomfort in my eyes, and even some gastrointestinal symptoms.
What was especially strange was that I eventually went back to the iPhone 15 Pro Max—the exact model I had previously used for around two years without major problems—and I started experiencing symptoms from that phone as well.
This made me think that some kind of sensitization may be involved. Once a strong reaction has been triggered by a particularly problematic device, the nervous system may remain on high alert, especially in people who are already prone to this type of sensitivity. After that, even relatively mild visual stimuli may be enough to cause symptoms.
Recently, I took a proper break from irritating OLED screens. When I returned to the iPhone 15 Pro Max, I limited the refresh rate to 60 Hz and disabled as many animations and visual effects as possible. Now I’m able to use it again.
So, for at least some people, it may not simply be a question of whether a particular phone is “safe” or “unsafe.” You may need to give your nervous system enough time to calm down and recover before testing OLED screens again.
Taking a complete break for several days—or perhaps longer—and using only a comfortable IPS display during that period may help. Afterward, you can gradually return to devices with better PWM and flicker characteristics, possibly starting with 60 Hz and reduced animations.
My theory is that this kind of break may help raise your tolerance threshold again. Of course, this is only based on my personal experience, but it may be worth trying if you suddenly find that every OLED phone causes symptoms, including devices you were previously able to use.
Posting this here in hope someone can help figuring this out.
I first noticed I was sensitive to certain types of screen when changing to a MacBook Air M3 13'' back in August 2024. It gave me severe eyestrain and headaches, it was unusable for me. I went back to my laptop.
Last year my Redmi Note 11 broke and I tried to find a new phone. I've tried:
- iPhone 12
- Redmi Note 14 Pro
- Redmi Note 13
- Redmi 14C (IPS LCD Screen
- Honor 200
Nothing worked for me. After using it for 30 minutes, I feel my head becoming heavy (what I feel is like a pressure). The day after, I still wake up with the headache and eyes very dry.
At first I thought PWM was the issue, but clearly not. Redmi 14C doesn't have it. Well, the MBA M3 neither.
I ended up buying a new Redmi Note 11. It gave me some headaches for a couple of days but then it was fine. Maybe I could have insisted on the other phones I've tried.
Now it's been a year and I'm trying to find a new phone before mine stops working.
I don't care about having a good phone now, just something that won't make me feel sick.
I've recently tried my husband's iPhone 13 mini and it makes me dizzy after using it for 30 minutes. And also his new iPhone 14 which is unbearable for me. I would use his old phone sometimes to take pictures, check Google maps or video chat with family and it wasn't an issue. But his new iPhone gives me headaches after using it just to take a few pictures or have a short video call.
I've tried iPhone SE 2022 just now. I used it for 30 times and feel a pressure in my head. I could only find it with iOS 26.
I would appreciate any help and input.
Some phones recommended here are not available in my country. I am in Portugal and will try only refurbed phones so I can return it when needed. New phones are not easy to return here.
