I’ve been on record here many times discussing why I can’t stand OLED screens. I was hoping the flickering, strobing effect was the result of cheap Android panels, but I can’t even look at an iPhone X or XS for more than a few seconds without feeling pain in my eyes, and the start of a headache within a few minutes.

fzslm and TheSpiceIsLife explained on Hacker News:

The OLED display on the X uses pulse-width modulation, which is basically where the OLED panel [varies the duty cycle] to adjust its brightness. Most people (like me) don’t really notice it, but for some it can cause headaches over prolonged use, and in some extreme cases really bad migraines.

Oleg Afonin went in to detail last March about the issue:

The iPhone X uses a new (for Apple) display technology. For the first time ever, Apple went with an OLED display instead of the IPS panels used in all other iPhones. While OLED displays have numerous benefits such as the true blacks and wide color gamut, the majority of OLED displays (particularly those made by Samsung) tend to flicker. The flickering is particularly visible at low brightness levels, causing eyestrain and headaches to sensitive users. Very few users have the slightest idea of what’s going on, attributing these health issues to oversaturated colors, the oh-so-harmful blue light and anything but OLED flickering.

He went into further detail about finding the sweet spot for brightness where your phone won’t flicker, and reducing the colour saturation in a follow up post. As IPS LCDs are less bright and have lower colour saturation anyway, it seems to me they would be a better choice for those of us sensitive to them.

This is the main reason I’m relieved the iPhone XR exists. An IPS display is objectively better because they’re crisper, but they also don’t flicker. I hope Apple continues to make a more affordable, LCD phone for when my iPhone 8 needs upgrading in a few years.