Why do some car headlights flash on and off when filmed in slowmo, eg on top gear?
In: Technology
Those are LED headlights, and LED’s aren’t just hooked up directly to a battery the way that incandescent bulbs are. They are driven by a small microchip which basically pulses power to them in order to control brightness and protect the LED from overheating. Incandescent headlights also use separate filaments or bulbs for high and low beams, where LED’s just change the frequency of the pulses to increase brightness.
Now when things get filmed it’s done in by taking a lot of pictures very quickly. When you film something that is blinking at a high rate, sometimes some of those pictures in the film catch the LED’s when they’re in the off state, hence the flickering.
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