> For the complete documentation index, see [llms.txt](https://docs.sevenpens.com/drawtab/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.sevenpens.com/drawtab/core/pwm-flicker.md).

# 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](/drawtab/process/measuring/measuring-pwm-flicker.md).

## Resources

* [RTINGS - Backlight strobing](https://www.rtings.com/monitor/tests/motion/black-frame-insertion)