I’m a small phone person. I have narrow hands and jeans with tiny pockets. That’s mostly why I hung onto my first generation iPhone SE for a very long time. But I’ve been longing for a phone with more up-to-date features—particularly a great camera. And once I was vaccinated, going to stores again, and contemplating seeing family and friends—and taking their pictures—getting a new phone seemed suddenly urgent. So, after checking out my options, the iPhone 12 Mini seemed like it would be the perfect phone for me—slim for my small hands, full of the latest features, including a highly rated camera system. And—the icing on the cake—an about-to-be released version came in my favorite color, a sort of blue/purple (think wisteria).
So I preordered a purple iPhone 12 Mini and picked it up two days later. I turned it on, looked lovingly at the home screen…. and burped. I burped again. My head started feeling fuzzy. I put the phone down fast. I knew I was feeling the first symptoms of motion sickness, and could soon be feeling more than a little uncomfortable.
After my equilibrium came back a little, I picked up the phone again and powered through the discomfort to check the accessibility settings. I had had motion issues with an earlier phone at one point, and knew to turn off motion effects to solve that problem. Maybe they had somehow turned back on? But no, my settings had ported over to the new phone. However, the feelings of disequilibrium weren’t going away.
I spent a week pushing through those sensations in sessions as long as I could take, hopeful that I was simply dealing with an adjustment issue, like that faced with new glasses. Because, other than the fact that it was making me sick, I really loved this phone.
But the nausea didn’t get any better. In fact, it had started to color my entire day with a constant state of discomfort.
So I turned to Google to find out why (using my laptop, not my phone). There were plenty of discussions about the iPhone 12 series and motion sickness—on Reddit, on the Apple discussion site—and it was mentioned as a possibility by a few review sites. Some of the suggestions for fixes were wacky (turn off the 5G; I confess, I tried it, I was ready to try anything. That didn’t help). Oddly, I found little real research about the problem; hard to believe, given the amount of anecdotal online chatter.
People who chimed into the various threads who seemed to know something about the subject put the blame on what is called Pulse Width Modulation (PWM), which is used to digitally control the brightness of every sub-pixel in the display.
PWM is one of two ways to dim a display; the other is by changing the voltage of every sub-pixel—the analog method. LG uses this approach to adjust brightness for its OLED TVs. For PWM, dimming involves rapidly turning pixels on and off; for 50 percent brightness, the pixels are on only half of the time. At high enough speeds, most people won’t be aware of any flicker or be affected by subliminal flicker, which may be the bigger issue.
Why not simply use the analog voltage control method? Well, for one, it’s much less power efficient than turning the display sub-pixels off for even the smallest amount of time, and better power efficiency means longer time between charges.
To confirm that PWM was the culprit for my motion sickness, I tried using the phone at different brightness levels, since the lower the brightness, the bigger the PWM effects. And, indeed, my level of nausea seemed to correspond directly to the brightness level.
The suggested fix: set the brightness up a high as possible, and leave it there—with less dimming, there should be less flicker.
And indeed, that helped a little. It made reading black-and-white pages, like emails and texts, tolerable. But for photographic images, which have a wide range of brightness, the motion sickness persisted, even at full brightness. That pretty much meant no social media for me—which, I briefly rationalized, could be a good thing.
But having a phone that even occasionally triggers motion sickness is really not such a great idea. And the clock was ticking on my 2-week return window.
With regret, I exchanged my wisteria-purple iPhone 12 Mini for a far less attractive and comfortable to hold second-generation iPhone SE, with an LCD display. And I soon was feeling back to normal. The iPhone SE may not have the latest and greatest features, but at least it doesn’t make me want to vomit. (I’ve lived in the iPhone ecosystem too long to start shopping beyond it, at least for now.)
Though I gave up the iPhone 12, I was left with a lot of questions. As more and more phones move to OLED displays, will I fall further and further behind? Why aren’t manufacturers doing anything about this? Am I in such a small minority that I don’t matter, or are there many of us out there, silently suffering or simply avoiding OLED displays?
I turned to Raymond Soneira, founder and CEO of DisplayMate Technologies, for some answers. Soneira, who has a PhD in theoretical physics, was a long-term member of the Institute for Advanced Study in Princeton, N.J., and then a principal investigator at AT&T Bell Laboratories’ Computer Systems Research Laboratory. He started DisplayMate Technologies in 1990; it helps display and device manufacturers optimize display performance and accuracy through testing, measurements, and mathematical modeling and analysis.
IEEE Spectrum: Am I alone—or part of a small minority—in my sensitivity to flicker?
Raymond Soneira: I’ve gotten hundreds of inquiries over the years regarding this issue, with people complaining of display flicker causing a wide range of symptoms, from visual fatigue, to headaches and nausea, up through seizures and photo-triggered epilepsy—which is the extreme version of flicker sensitivity. In many cases the flicker is subliminal. Some people just feel unusually tired or uncomfortable and don't know why.
All display technologies can have flicker issues. Back in the days of CRTs, interlaced flicker drove everyone mad, though if you sat back far enough from your TV, like your mother told you, it wasn’t an issue. LCD displays, which are now all backlit by LEDs, do use PWM, but it’s the backlight that flickers, and it somehow doesn’t seem to trigger as many visual issues [as OLED], perhaps because it’s typically done at much higher frequencies. Also, LCD displays have a much slower pixel response time compared to other technologies, which reduces the amount of on-screen flicker. So right now, it’s mostly the OLED displays that I’m hearing about regarding this issue.
I’ve gotten emails from well-known television anchors and newspaper columnists, and many others that have told me exactly what you have said. ‘I use my phone, and half an hour later I feel ill.’ I’ve had enough people that I’ve known within the display industry tell me they have these issues, so I know it’s a real effect.
They all ask me what to do. And the answer is, as you figured out, just return it and try another display.
Is it every OLED phone display that’s a problem, or just some of them?
It’s complicated. Some phone manufacturers will take an off-the-shelf display and park it inside their phones and use all the display manufacturer's default settings. Others, like Apple, for example, significantly modify the drive electronics and firmware.
Typically, the rate of PWM is four times the refresh rate of the display, so for a high-end 120 Hz display, the flicker is 480 Hz. That’s generally thought to be beyond what most people can perceive, though some people can sense even that. But it’s not always a direct relationship. Even if the hardware refresh cycle is 120 Hz, some of the image content on the screen can be updating at a slower rate, say, when you are scrolling or streaming video, and are processor and/or bandwidth limited. So the image flicker can be much slower than the 120 Hz refresh rate.
Also, a manufacturer can choose to update a display via a combination of rows and columns, or specialized patterns—this can be a factor in producing flicker. It’s possible that if you update sections of the display at different times, rather than the whole display at once, it may not trigger the flicker issue.
The iPhone 12 series has a 60 Hz refresh rate, so the PWM rate is likely 4 times that, or 240 Hz. [The slower the flicker, the more likely people are to be affected by it.]
Am I going to be shut out of future phone upgrades? I don’t see many of the top-of-the-line models coming out with LCD displays.
Indeed, the high-end flagship displays worldwide are now almost all OLED displays. But some OLED displays already use a combination of analog brightness together with PWM, which helps. Also, I have heard from some high end manufacturers recently who are looking into how they can make a high-end LCD display compete on image accuracy and color accuracy with OLEDs.
Is anybody doing real research into the problem, in terms of how many people are affected and how to prevent it?
The Chinese government may be, it is very concerned about their children’s eye development because they spend too many hours in front of displays, and they have set some requirements for displays. A number of research hospitals and ophthalmologists have contacted me with questions on display technology issues regarding this problem, so there is work in this area.
This issue concerns me a lot. I would like to see manufacturers pay a lot more attention to how displays affect human vision, and then how to improve them. We have only been using displays for some 70 years, so we still have a lot to learn, especially now that so many people are spending many hours per day in front of their smartphones, computer monitors, and TVs. Some of it is undoubtedly related to the specifics of a particular model and a particular technology, but we really don’t know enough. Manufacturers clam up on this with me; they don’t want to talk about these issues.
From my end, just about the only issue I don’t test displays for is flicker sensitivity, other than measuring the refresh and PWM rates, since it is very hard to quantify.
With your now-known sensitivity to flicker, you could perform an important public service: Go to a local phone store and test how you respond to all the different displays and then publish the results.
I just may do that.
Tekla S. Perry is a senior editor at IEEE Spectrum. Based in Palo Alto, Calif., she's been covering the people, companies, and technology that make Silicon Valley a special place for more than 40 years. An IEEE member, she holds a bachelor's degree in journalism from Michigan State University.