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PWM flicker

Overview

PWM flicker is a visual artifact in certain displays that some people can see.

  • Not all displays exhibit PWM flicker

  • Not all people are equally sensitive to flicker.

  • For a given display, one person may not detect the flicker, while others might see it clearly.

  • Since not everyone can see it, we have to use equipment such as a smartphone to help detect whether a display has it.

  • Some people cannot see it, but they are still affected by it.

Naming and terminology

  • PWM stands for Pulse Width Modulation

  • You may see this referred to as "PWM dimming"

Background

Display panels have techniques to regulate their brightness levels:

  • PWM - Turning the entire display on and off rapidly. Ideally, the frequency is so high that a viewer cannot see it.

  • DC dimming - Instead of turning off the display, less power is sent to the display.

What determines whether the flickering will be seen

  • The PWM frequency. The higher the frequency, the less likely someone is to notice flicker.

  • Differences in individual eyes and brains. Some people are simply more sensitive to the effect.

Headaches

Besides being visible and irritating, flicker may produce headaches for some people. Some people say they cannot see PWM flicker, but they still get headaches from it.

Testing tablets for PWM flicker

How I measure it: Measuring PWM Flicker.

Resources

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