I have seen several videos and I myself filmed couple near the gas station prices and wonder why this happens?
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If the display in question is something like a flat panel display or looks like a giant television, that’s because the screen’s refresh rate is different from the camera’s recording speed. This can manifest in the form of black bars traveling up or down the display, or other visual artifacts.
If you’re talking about a screen that uses LEDs in a pattern, like a standard LED numeric display, that’s because the circuitry driving them actually pulses the current to the LEDs. This lets them be driven to be apparently brighter while not burning them out or requiring more expensive LEDs that can handle higher power or work continuously at greater brightness.
Normally our eyes don’t see the flicker, but a camera can capture the effect, again usually because of capture speed being different than the update frequency of the pulsed LEDs.
You’ll see a similar effect in some car headlights and many other devices that use LEDs, most especially with LEDs whose brightness can be varied- that’s done by changing the pulse width to make the LED be “on” more or less, changing its apparent brightness to the human eye.
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