Like the previous generation of iPhones, the iPhone 17 range employs OLED panels that are prone to flickering, which some people are sensitive to. The flickering is caused by PWM (Pulse Width Modulation), a technology used by OLED manufacturers to control display brightness. The screen flickering is particularly visible in low ambient brightness conditions, and may cause eyestrain with sensitive users. Fortunately, in this generation Apple provided a simple solution to get rid of the flickering by finally adding the DC Dimming option.

TL&DR

If you don’t want to waste time reading the article and just want to disable PWM flickering at low brightness, just do the following: open Settings > Accessibility > Display and Text Size and enable the “Display Pulse Smoothing” setting. Once you do that, your iPhone will reportedly stop flickering (currently only under 25% brightness). Note that this setting and “Reduce White Point” are mutually exclusive; when you activate “Reduce White Point”, “Display Pulse Smoothing” gets disabled (and not automatically re-enabled).

The name of the setting is somewhat misleading. Here’s how Apple themselves describe the “Display Pulse Smoothing” option:

“Disables pulse width modulation to provide a different way to dim the OLED display, which can create a smoother display output at low brightness levels. Disabling PWM may affect low brightness display performance under certain conditions.”

What is PWM flickering and how does it look?

Check our old article about iPhone X Eye Strain. We have graphs and screenshots and scientific explanations of the issue. Since PWM didn’t really change much since that time, we decided against reprinting it here.

Can I do that on older iPhones?

No, not this, not exactly. However, you can still reduce PWM flickering at low brightness by reducing white point and assigning a convenient shortcut (like triple-pressing the power button) to turn it on and off.

Any drawbacks?

So the positive side of disabling PWM-based brightness control and enabling DC dimming instead is obvious: less eyestrain and less fatigue for everyone, and not just to those who consciously notice flickering. This translates into more comfortable long-term use of the phone, especially for reading, gaming, or other activities where extended screen time is unavoidable. Additionally, DC dimming can help create a more natural perception of brightness changes, since it avoids the micro-pulses of light intensity inherent to PWM, leading to a steadier and more visually consistent image and potentially smoother perceived scrolling experience.

However, DC dimming is not without its compromises. Because it works by reducing the voltage supplied to the display’s OLED panel rather than modulating on-off cycles, it can sometimes affect color accuracy, especially at lower brightness levels (this is perhaps what Apple had in mind when they mentioned certain conditions in the feature description). In older, lower-quality OLED panels, DC dimming can also introduce uneven brightness across the screen, leading to stability issues such as color shifting or banding; below is the image of an ancient DC-dimmed phone LG G Flex 2:

Now, that phone was released in 2015, and since then OLED panels had substantial progress, so this is no longer applicable to the new generation of iPhones.

Another thing potentially affected by DC dimming is ghosting or black smearing, which is a shadow-like artefact that appears when you scroll white text on a black or grey background. On lower-quality OLED displays with longer LED switch times this effect is more likely to show up at lower brightness under DC dimming than under PWM, where pixel response times stay more consistent. This, again, is hardly applicable to the responsive OLED panels installed in newer iPhones.

Finally, DC dimming may affect color reproduction at very low brightness level. This, however, can be practically dismissed as you are probably less likely to require studio-grade color fidelity at night or at very low levels of brightness.

Additional information

Since the introduction of the iPhone X back in 2017, which was the first Apple device to use an OLED panel, we were constantly trying to find ways to reduce PWM-induced flickering. Finally, this issue is seemingly coming to an end, at least to a degree (unless Apple backtracks the feature later on for whatever reasons).

• iPhone X Eye Strain: How to Stop OLED Flickering in Just Three Clicks
• iPhone Xs PWM Demystified: How to Reduce Eyestrain by Disabling iPhone Xs and Xs Max Display Flicker
• Using DC Dimming to Stop PWM Flickering in iPhone 11 Pro and Pro Max, Google Pixel 4 and 4 XL