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OMD video issue


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#1 edmond320

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Posted 07 October 2012 - 07:18 PM

[youtubehd]dtasDLgYKlg[/youtubehd]
Can anyone help me?
A night dive video at Lembeh with OMD, the video appear strange with horizontal scanning movement.
What is that ?
My setting for video is 1920x1080 fine, with a single LED video light.
The raw .mov file play with Olympus viewer 2 appear the same.

Thank you.

Regards
Edmond

#2 r4e

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Posted 07 October 2012 - 07:45 PM

A night dive video at Lembeh with OMD, the video appear strange with horizontal scanning movement.
What is that ?

My guess is that this is interference between exposure time and the (adjustable) LED lamp. Especially adjustable lamps are likely to have pulse width modulation (PWM) to adjust the brightness of the lamp. In this case the PWM frequency is in the same range as the exposure time of the camera. You should be able to get rid of the interference either by a) adjusting your lamp to max intensity (continuous light) or b) by lengthening the exposure time of your camera. For both of these, you'll need to adjust the sensitivity or gain of the camera.

Edited by r4e, 07 October 2012 - 07:46 PM.

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#3 edmond320

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Posted 07 October 2012 - 11:55 PM

Hi r4e,
Thank you very much for your information, will adjust it accordingly to remove the flickering.
Thank you !!

Regards
Edmond

#4 Steve Douglas

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Posted 13 October 2012 - 03:03 PM

This is one I have never seen before. R4e presents a good explanation..thanks. Always learniing
Steve

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#5 Nick Hope

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Posted 13 October 2012 - 09:55 PM

What light were you using Edmond?

#6 Drew

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Posted 14 October 2012 - 08:58 AM

Yup, shutter speed. From the looks of things, you probably need to set it to 1/50 or 1/60 (or multiples of them) to match the 100 or 120hz of the LED light source. Same for fluorescent lights etc. Cameras can "catch" the flicker, which gives that effect.

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#7 Steve Douglas

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Posted 14 October 2012 - 09:36 AM

I wonder if a 'rolling shutter' filter might fix the issue in the footage. I tend to doubt it but it would be worth the experiment.

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