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Old December 19th, 2011, 04:04 PM   #1
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black horizontal "banding"

I recently shoot some footage for a wedding, using a 1.2 50mm lens at 1600 iso.

Can anyone tell me what is causing the weird think black vertical "banding" (I think this would be the appropriate term for this phenomenon?)?

is it just an unavoidable function of shooting in low light at high iso with this camera?

it is most evident around the 30 second mark, if you look in his white shirt.

thanks in advance.


Last edited by Todd Sheridan; December 20th, 2011 at 03:04 PM. Reason: typo in title
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Old December 19th, 2011, 05:36 PM   #2
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Re: back vertical "banding"

I've never seen that purely due to high ISO... under certain light sources something similar occurs due to a slight phasing between the light's flicker frequency and the scanning of the image, similar to filming an old television tube. I've never seen it produce bands with such sharply defined edges though, so it's possible it's an issue with the camera itself.
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Old December 19th, 2011, 05:48 PM   #3
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Re: back vertical "banding"

Quote:
Originally Posted by Evan Donn View Post
I've never seen that purely due to high ISO... under certain light sources something similar occurs due to a slight phasing between the light's flicker frequency and the scanning of the image, similar to filming an old television tube. I've never seen it produce bands with such sharply defined edges though, so it's possible it's an issue with the camera itself.
This is correct. I'd wager you shot under fluorescent lights. I'll also wager you shot at a shutter speed faster than 1/60th of a second. Because fluorescent lights cycle on and off many times per second you can catch them, with a fast enough shutter peed, at a time when they spend more time off than on. This can also introduce bands of color, not just brightness, as there are different phosphors within the light that are "turned on" at different points in cycling the power and exiting the mercury gas. In a CCD you'd experience this globally, i.e. across the entire image, but since you are shooting CMOS, it rolls through the image in bands.

Solution: Shoot a slower shutter speed or get better fluorescents. Considering you're at an event, I don't think the latter is feasible ;)
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Old December 19th, 2011, 06:16 PM   #4
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Re: back vertical "banding"

I definitely shot at 1/60th, 24fps. and there were no fluorescent lights in the venue, at least not overhead. maybe some spillage from the bar, but I doubt even that. it was a very dark room lit with incandescent bulbs and candles.

weird stuff.
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Old December 19th, 2011, 08:56 PM   #5
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Re: back vertical "banding"

My money is on the stage lights which might be discharge lamps, flourescent tubes or large panel video display. In one shot, the intensity of the banding changed, either due to somebody stepping in front of the source, or the brightness of an image on a display changing due to to the image changing.

Just a wild guess. The camera seems fine. It is one of those live within your means things. I think you are likely well pleased with the other attributes of the camera.
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Old December 19th, 2011, 09:05 PM   #6
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Re: back vertical "banding"

makes sense.
thanks everyone.
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Old December 20th, 2011, 03:03 PM   #7
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Re: back vertical "banding"

by the way, my title should read "black horizontal "banding"", not "back vertical banding".

no more pre-coffee postings.
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Old December 20th, 2011, 03:43 PM   #8
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Re: back vertical "banding"

You might try a test with similar settings and incandescent lighting (or even better, filtered sunlight) shooting a blank wall. It's possible that your camera has some interference due to bad shielding or a bad connection. It's possible that this was caused by strange lighting, but if not, you'd want to know it and get it repaired before your next shoot. If you can't re-produce it, then chalk it up to the lights.
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Old December 24th, 2011, 05:08 PM   #9
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Re: back vertical "banding"

It certainly has something to do with a 50 or 60 hz light source (probably on stage) , but in any case it is much less disturbing than the awful rolling shutter effect of photoflashes going off.
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