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flashing daytime running lights


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In cars, LEDs are modulated, and therefore are flashing very rapidly. This is not perceivable to the naked eye, but the recording rate for video (in fps) and are not in sync with the frequency that the LEDs modulate. Professional videographers can't get away from this effect. We have a security camera system at the fire station and when I pull up, they say my LED DRL's are flickering in the cameras.  It's kinda like when a helicopter is being filmed and it looks like the rotor blades are stopped or change directions.  A lot of mfg.'s today still use halogen reverse lights instead of LED's to prevent flickering in back up cameras.

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Yep the LED's are driven by pulse width modulation (turned on and off very quickly) to control their light output aka dimming. The reasons for this vary and some are complicated. It's common with most LED DRL's and even LED brake lights use PWM. 

Edited by HondaHawkGT
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On 7/7/2019 at 2:18 PM, mafd2 said:

In cars, LEDs are modulated, and therefore are flashing very rapidly. This is not perceivable to the naked eye, but the recording rate for video (in fps) and are not in sync with the frequency that the LEDs modulate. Professional videographers can't get away from this effect. We have a security camera system at the fire station and when I pull up, they say my LED DRL's are flickering in the cameras.  It's kinda like when a helicopter is being filmed and it looks like the rotor blades are stopped or change directions.  A lot of mfg.'s today still use halogen reverse lights instead of LED's to prevent flickering in back up cameras.

I was able to get around that by reducing the shutter speed in the video. I cut down the ISO to 50 (to make it darker) and lowered the shutter to 1/60 (to catch all the LED). If I shake the camera a lot, there will be a lot of motion blurs, but at least I get LED lights in my videos. So it's either video blurs or weird LED effects.

Edited by Wiggums
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