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LED's flicker free?


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#1 Austin Schmidt

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Posted 02 April 2011 - 05:59 PM

I'm potentially using American DJ megabar LED's for a music video in which we will be shooting up to 120fps with a shutter of 90 and 45. I realize consumer LED's have a flicker undetectable to the human eye, but assume they would be noticeable at higher frame rates. Is this the case for professionally built theatrical lights as well such as these specific megabar LED's? I'll be doing tests this week, but was looking for any outside perspective. Is it just a matter of shooting at 60hz safe frame rate/and shutter angles when it comes to LED's?
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#2 Matthew Parnell

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Posted 02 April 2011 - 09:09 PM

A lot of LED units flicker because manufacturers dont bother using fully regulated DC driver units. A lot of the time in consumer units, LEDs are either driven using DC that is just rectified AC, or a poorly regulated version of the later. Some also use poor quality switch mode units that can cause flicker at unusual rates.

There are quiet a few theatrical LED Units that do flicker. Especially as you head towards the cheaper and older stuff. It would be really worth doing some tests, especially with the LEDs dimmed and set on different colours to work out what is the best approach, and whether you can use the units. When you do the tests make sure you also pan through the lamps at different rates as well, some LED flicker is most apparent when movement is involved.

Quiet a few, but sadly not all the LEDs that flicker, flicker at the same frequency as the mains they are supplied with, so dont assume that running your camera at 60hz flicker safe speeds is the solution to all LED flicker evil.
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#3 Mitch Gross

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Posted 08 April 2011 - 12:49 AM

Most important is not to dim the LEDs, as most fixtures use pulse modulation to control brightness.
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