Modern smartphones are built with different screen technologies, with high-end models featuring OLED and AMOLED screens. The screen type of a smartphone does matter, especially if you stream content a lot or play mobile games, but you know what matters the most? The display technology.
Not many people know about the Pulse-Width Modulation (PWM) display technology used by most smartphones, and that could even be the cause of the strain you always feel when using your smartphone. PWM is a screen dimming technology that tricks your eyes to believe your display was just dimmed, while in the real sense, nothing happened. Sounds confusing? Now let’s get to the details.
What Exactly is Pulse-Width Modulation (PWM)?
You see, oftentimes, when the smartphone display topic is brought up, the focus is usually on the resolution pixels, OLED or AMOLED selection, bit brightness, and whether it’s made from Corning Gorilla glass, leaving out the real concerns like PWM. Yes, not all smartphones have PWM, and for those that have it, in most of them, you cannot turn it off.
PWM, which is the acronym for Pulse Width Modulation, is a display technique used by smartphone manufacturers to control screen brightness—especially on OLED and AMOLED panels. The technology works by making the smartphone’s screen flicker rapidly (by turning pixels on and off in cycles) instead of directly lowering the pixel brightness.
However, the flickering, triggered by PWM, happens so fast (hundreds to thousands of times per second) that your eye cannot naturally capture it as it happens. But even at that, sensitive users may still notice the effects and start getting strains. Put simply, if you always feel headaches or your eyes hurt after looking at your phone’s screen for a while, PWM could be the culprit. Pulse Width Modulation works in this manner:
- When pixels stay “on” for a long time, the screen looks brighter.
- When they stay “off” longer, the screen appears dimmer.
How Does PMW Work?
PMW mainly triggers at high brightness and low brightness; it is more noticeable at low brightness levels than in high brightness levels. Apparently, PMW works in contrast to DC dimming, which is the alternative screen dimming technology for LED screens.
The higher the screen refresh rate, the better (and safer) it is for PMW-sensitive users. When the PWM frequency is too low (somewhere below 200Hz or less), some users may experience headaches or eye strain. The reason? That’s because at low frequencies, the rapid on-off pixel cycles become more noticeable and can cause visible flickering.
On the other hand, very high PWM frequency means that the flickering will happen too fast for your eyes to capture it, which is a good thing by the way, but doesn’t eliminate the fact that your brain did pick the flickering and acted on it, so you may still feel a strain in a while.
Also, the sad news is that many phones have low PWM frequency (below 500Hz), including Samsung and iPhone high-end models. In fact, only Motorola (with the Moto Edge Plus 2023) introduced the option to turn off PMW entirely, while the likes of Realme (with the Realme 10 Pro+) introduced a whopping 2160Hz screen frequency, which significantly reduces the impact of PMW flickering for the user—but still doesn’t eliminate it entirely for sensitive users.
Most smartphone manufacturers have started working on offering higher screen refresh rates and PMW frequency, as well as an option to turn off PMW. But in the meantime, if your device uses PMW and you’re sensitive to it, it’d be best to not use the device in a totally dark room—keep the lights on. Also, turn off automatic brightness and manually set the screen’s brightness to a level that feels comfortable for your eyes.
Which Smartphones Use PWM Dimming?
While our focus is on smartphones, it is important to note that PWM is equally used in other devices that feature displays, such as televisions (both smart and non-smart), tablets, monitors, and many other devices. It is actually a low-cost method for dimming OLED screens, hence the rapid adoption by OEMs.
That said, PWM is common in OLED and AMOLED screens; so, if your device screen is OLED or AMOLED, chances are that PWM is integrated into the display, whether it’s mid-range or high-end. So to say, Apple iPhones, Google Pixels, Redmi Note series, Samsung Galaxies, and even OnePlus devices come with this technology.
Some known models to integrate PWM are:
- All iPhones with OLED displays (from iPhone X onwards, except the SE series)
- Samsung Galaxy S, Z Fold/Flip, and many A-series models.
- Google Pixel 6, Pixel 7, Pixel 8, and newer
Interestingly, LCD-based smartphones rarely use PWM because LCD panels dim their backlights differently.
Is PWM an Important Feature?
Actually, PMW ensures accurate colors at different brightness levels and helps to conserve battery life, compared with DC dimming. But nope, PWM is not exactly an important feature; it was simply a breakthrough OLED display technology for display engineers, and now, the same engineers are looking for ways to better the tech, since it’s harmful to many people.
Is PWM a High-End Feature?
No, it is not. But, it is only present in devices that use OLED screens, and yes, most devices that use OLED are high-end. So, it’s not the PMW itself that is high-end, but the display—OLED. PWM is equally available in budget and mid-range smartphones, provided they are built with OLED displays.
Notwithstanding, with the fuss about PMW being hurtful to the eye, some manufacturers now add a “high-frequency PWM dimming” note (like 1920Hz or even 2160Hz) into the specs sheet of their devices. This is because higher frequencies make flicker less noticeable to the human eye, and OEMs market it as a comfort-oriented feature.
Why Is PWM Bad for Some People?
Some people are very sensitive to a lot of things. The display flickering caused by PMW is definitely a “big deal” for some people because it causes them eye strain, headaches, fatigue, dizziness, or even nausea in extreme cases, especially when they actually reduce their device’s brightness thinking that was where the problem lie, unknown to them that PMW is agressive on lower brightness on screens with frequencies below 500Hz.
Can PWM Be Turned Off?
It actually can, but the option is only available on very few smartphones—with the Motorola Edge Plus 2023 being the only known at the moment to offer that turn-off option. For most other smartphones, you can’t disable PWM completely; what you can do is work around it; for example, you can keep your screen brightness level at 50% to reduce the impact, or use third-party apps to overlay brightness filters. Also, some smartphones offer options to switch from PMW to DC dimming. But, in all, Apple iPhones currently do not offer these options.
What More?
Well, you can simply purchase a smartphone that uses LCD instead of OLED or AMOLED. If you must stick with OLED-powered smartphones, then go with models that have high-frequency PWM OLEDs like the iPhone 14 & 15 Pro, Xiaomi 13 Ultra, and a number of others. Other display tech like mini-LED and e-Ink panels avoid PWM flicker, but these are rare in smartphones. Hope you learnt something today?
