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LED Lighting at 24fps


Bill DiPietra
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I'm going to be doing a shot that has emergency lights reflected off of a house. I've found a decent set of LED emergency lights, but I've never used LED lighting on film. I believe the lights connect to the cigarette lighter socket of a car. Can anyone tell me if I am likely to get any kind of weird flicker?

 

Thanks.

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You shouldn't get mains flicker from a DC source, but I had a show a couple of years ago where we tried to use a LED Emergency beacon. It turned out that the flash of the beacon was of sufficiently short duration to cause rolling shutter artifacts. This may or may not be a problem for you.

 

That's good to know. Thanks, Stuart. This one has different rates that it can be set to, from fast to slow.

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Why 'leds' may give a pulsing 'light' effect, is due to how LEDs are handled electronically. Usually a short high voltage pulse is applied, since that yields a higher lumen value, than a 'steady state' voltage. Provided the duty cycle is such that the LED does not burnout.

 

However, this can produce problems in cameras that are scanning out regions of the sensor, depending.

 

I've never tested this out, relative to effect on Digital film... but I have noticed that if I see brake lights that when I avert my eyes, I see a sort of 'pulse stutter', rather than a smooth blur (what else are you going to do at a traffic light...), that the brake light is most likely pulsed LED.

Edited by John E Clark
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