Sometimes, these monitors will use a technique called pulse width modulation in order to dim the backlight, where it sends short impulses, creating a flicker effect. LED-backlit monitors have a backlight to display an image on the screen. Still, OLED monitors get a perfect 10 because they don't have any flicker.

This test is meant for LED-backlit displays and not OLEDs because they don't have a backlight.

You can use the test above to see when the flicker starts exactly.

We test the flicker on TVs similar to monitors, but on TVs, we also check to see which backlight setting the flicker starts at.

If you don't see this effect, then there's no flicker. Increase the backlight until you don't see this. If you notice your hand is moving like it's in front of a strobe light, then it has flicker. If you're concerned that your monitor flickers at lower backlight levels, set the brightness setting to its lowest, and wave your hand (or any object) in front of the screen.

A monitor can introduce image flicker at lower backlight levels, even if it's flicker-free at its max brightness.480Hz flicker - Vizio D3 Series 2021 Other Notes

Flicker photo