Why do LED headlights flicker when being viewed through a camera or recorded video but not when you look at them with a naked eye?
In: Technology
Pulse width modulation: keeping LED’s on for a short burst, and off for a short burst (usually shorter off times) to save electricity, reduce heat output, and create a ‘dimming’ effect for LED’s, because LED’s can’t be dimmed by lowering voltage.
So when an LED is on a PWM circuit, and a camera records it, the light will blink on the recording/playback, because the LED is blinking at a different rate that the camera shutter speed is capturing the video.
If you have the ability to ‘shake your eyes (see ‘nystagmus’) you can see the effect IRL, or if you look toward, or away from a set of taillights of cars that have this effect (Cadillacs have, im my opinion, the best viewing ability for this effect) you’ll notice in your peripheral vision dots or dashes of light (depending on how fast you adjust your gaze)
They are flickering 50 or 60 times per second depending on the frequency of your mains current. Human eyes aren’t fast enough to notice it but cameras are.
If something flickers with a high enough frequency your naked eyes won’t see the flicker. That’s why you can see movies with 24 frames per second.
Thanks for the replies y’all. Makes sense.
Because that’s how LEDs control their brightness. They only work at a certain voltage, if you want a dim LED you can’t just turn down the voltage. Turning it down beyond a very small window of where the LEDs will work will just cause the LED to turn off. LED’s brightness is controlled by turning it on and off very quickly, faster than the eye can see.
Your brain always tries to patch up what the eyes see.
This is the same thing going on for all optical illusions.
The eye might see them both on and off but the brain patches it off and transmits a smooth, always on image.
The camera usually records from top to bottom so in the little time it takes to make a frame, some lights are on and others of and buy the time an other frame is taken, and other part of the led is on but the same part is off by the time the frame is fully recorded.
Thi give the flickering or snake type of Lighting.
Because LEDs are only on for like 1/60 of a second and are off for the remaining 59/60 of the second.
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