Turning off PWM flickering on the iPhone 17 is possible, but unlikely to bring benefits

Most OLED panels in current smartphones have pulse-width modulation (PWM), which is a method for controlling the average power of an electrical signal by digitally turning the screen on and off rapidly. This can be implemented more precisely, more energy-efficiently and also more cost-effectively than analog control.

Display Pulse Smoothing (PWM)

The problem with PWM is its low PWM frequencies, typically below 500 Hz. Sensitive people may perceive this as flickering, which can cause symptoms such as burning eyes, nausea and headaches, among others.

Hence, it is all the more welcome that Apple has given its new iPhones, including the Apple iPhone 17, an option that disables PWM dimming. Called Display Pulse Smoothing (PWM), it can be found in iOS 26 under Settings, Accessibility, and Display & Text Size.

Alternative dimming only up to a maximum of 25% brightness

As our Apple iPhone 17 review shows, users shouldn't expect too much from Apple's PWM option. It only works up to 25% screen brightness, and the dimming frequency doesn't change. At brightness levels above 25%, everything remains the same, as PWM dimming is still used.

Apple itself only vaguely describes what happens when display pulse smoothing is activated, calling it an "alternative method for dimming the OLED display". The manufacturer presumably uses a form of DC dimming or a hybrid solution, but does not provide any technical details.

In his video, YouTuber Nick Sutrich concludes that Apple uses pulse amplitude modulation (PAM) for display pulse smoothing. Unlike PWM, PAM changes the signal amplitude, i.e., the voltage level, which produces a sine wave-like signal curve instead of a square wave, resulting in smoother brightness transitions.

This effect can also be observed in our measurements. When display pulse smoothing is activated, the frequency response is significantly flatter up to display brightnesses of 25%.

Affected individuals do not notice any improvement

Regardless of which method is ultimately used, it seems to offer little help to PWM-sensitive users. For example, in the Reddit subpage r/PWM_Sensitive, there are numerous reports from users who, even after activating the dimming option, complain of the same symptoms they experienced with conventional PWM dimming.

The main reasons for the ineffectiveness of the display pulse smoothing option appear to be the unchanged dimming frequency and modulation rate compared to PWM dimming – precisely the factors that significantly contribute to PWM symptoms.

While it is commendable that Apple now offers a PWM option for its new iPhone lineup, it remains to be seen whether it will work more efficiently in the future and actually benefit PWM-sensitive users. Hopefully this comes sooner than later in the form of a software update, rather than with the next generation.

Read the full review of the Apple iPhone 17 here.