What Causes Flicker and Banding in Video?
Mains electricity alternates at 50 Hz in Europe, most of Asia, Africa and Australia, and 60 Hz in North America and parts of South America and Asia. Many LED and fluorescent lights pulse at twice that rate — 100 or 120 times per second.
If a camera’s exposure does not contain a whole number of those pulses, each frame catches a different amount of light. On a rolling-shutter sensor, where rows are exposed one after another, that shows up as dark horizontal bands rolling through the picture. On a global-shutter sensor the whole frame pulses brighter and darker instead.
How to Run the Flicker Test
- Read the photosensitivity warning, then choose a green preset — those frequencies are frame-locked to your display, so every pulse is identical.
- Go fullscreen, fill the camera frame with the screen and focus on it.
- Record video at the shutter speed you want to evaluate.
- Toggle the camera’s anti-flicker setting or change the shutter speed and compare: stable, evenly lit footage means that setting is flicker-safe.
Which Flicker Frequencies Can Your Monitor Show?
A screen changes once per refresh, so the fastest clean square wave is half the refresh rate, and only frequencies that divide evenly into it are perfectly regular. CamTestKit measures your display and marks those presets green.
| Display | Exact flicker frequencies |
|---|---|
| 60 Hz | 30, 15, 10, 7.5, 6, 5 Hz |
| 100 Hz | 50, 25 Hz … |
| 120 Hz | 60, 30, 20, 15, 12, 10 Hz |
| 144 Hz | 72, 36, 24, 18, 14.4, 12 Hz |
| 240 Hz | 120, 60, 40, 30, 24, 20 Hz |
To reproduce a 50 Hz (PAL) environment exactly you need a display running at 100 Hz; 60 Hz needs 120 Hz or 240 Hz.
Flicker-Safe Shutter Speeds for 50 Hz and 60 Hz Lighting
Choose an exposure that spans a whole number of light pulses. The calculator under the pattern works this out for any frequency.
| Mains | Light pulses | Flicker-safe shutter speeds |
|---|---|---|
| 50 Hz | 100 per second | 1/100, 1/50, 1/33, 1/25 s |
| 60 Hz | 120 per second | 1/120, 1/60, 1/40, 1/30 s |
How to Fix Flicker on a Webcam
- Set anti-flicker (powerline frequency) in the camera software — Logi Tune, Windows Camera settings or OBS “Video Capture Device” properties — to match your country.
- Lock the shutter to a flicker-safe value from the table above if your camera allows manual exposure.
- Replace cheap LED bulbs with flicker-free, DC-driven lights.
- Add more light so auto-exposure is not forced into long, uneven exposures.
Flicker Test FAQ
Why do I see horizontal bands in my video?
Your room lights pulse at twice the mains frequency and your camera’s rolling shutter exposes each row at a slightly different moment, so rows catch different parts of the pulse. Use a shutter speed that spans a whole number of pulses or set anti-flicker to your local mains frequency.
Should I set anti-flicker to 50 Hz or 60 Hz?
Match your mains frequency: 60 Hz in the United States, Canada, Mexico, South Korea, Taiwan and parts of South America and Japan; 50 Hz in most of Europe, Asia, Africa and Australia. If bands remain, try the other setting — some regions and generators differ.
Is the flicker test safe to look at?
Full-screen flashing can trigger seizures in people with photosensitive epilepsy. The test only starts after you confirm a warning. Point the camera at the screen rather than watching it, and do not use this mode if you are sensitive to flashing lights.
Why are 50 Hz and 60 Hz crossed out on my screen?
A 60 Hz monitor can only switch the image 60 times per second, so the fastest clean flicker it can show is 30 Hz. 50 Hz and 60 Hz need a 100 Hz or 120 Hz display respectively; the green presets are the frequencies your screen can render exactly.