What is temporal dithering?
A 6-bit panel can show 64 levels per color channel, about 262,000 colors. A true 8-bit panel shows 256 levels, about 16.7 million colors. To look like an 8-bit panel, many 6-bit screens use frame rate control (FRC): a pixel that should sit between two shades flips back and forth between them every frame or two, so your eye averages them into the shade in between.
That’s temporal dithering. The picture looks still, but many pixels are constantly flickering at a small scale. Some panels sold as 10-bit do the same thing on top of an 8-bit panel.
What does dithering sensitivity feel like?
People who believe they react to dithering describe eye strain, headaches, nausea, a shimmering or unsettled look to the screen, and trouble focusing. A common clue is that some devices are fine while others with similar brightness and color aren’t.
What does the research say?
Very little research has looked at FRC dithering directly, so it’s an open question. What is known points the same way: the retina responds to flicker well above the rate you can see,1 and flicker in lighting is linked to headaches and eye strain.2 The idea is plausible; it just hasn’t been properly studied yet.
Can my computer add dithering?
Yes. Some graphics cards and operating systems dither the picture before it ever reaches the monitor, especially when they process color. On some systems it can be turned off in the graphics driver settings. A monitor can only promise not to add dithering of its own.
How to avoid temporal dithering
- Check the panel’s real bit depth. Spec sheets often say “8-bit (6-bit + FRC)” or “10-bit (8-bit + FRC)”. You want a true 8-bit panel with no FRC.
- Turn off dithering in your graphics settings where your system allows it.
- Avoid PWM as well. Screens that dither often also pulse their backlight. See PWM sensitivity.