PWM Flicker

Overview

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

  • 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, others might see it clearly.

  • Since not everyone can see it, we have use equipment (like a smartphone) to help us detect whether 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 of turning the display on and off rapidly 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 any flicker.

  • Variances in individuals eyes/brains - some people are just more sensitive to the effect

Headaches

Besides being visible and irritating, the flicker may produce headaches for some people. Some people say they cannot see the PWM flicker, but this still get the headaches caused by the PWM flicker.

Testing tablets for PWM flicker

How I measure for it: Measuring PWM flicker.

Resources

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