> 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) --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.sevenpens.com/drawtab/core/pwm-flicker.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.