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Banding when shooting lightning

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Paul Bean
Banding when shooting lightning
on Sep 22, 2009 at 5:39:49 pm

Hey Guys and Gals,

A friend of mine shot some storms the other night with his EX-1 and
was disappointed to see horrible banding and glitching on every
lightning strike. Here is a clip of several strikes edited together.

http://vegasdigital.com/Lightning.mov

What you are seeing here is not compression artifacting. (Well
technically it could be but it would be in-camera and not a result of
compressing this file for internet distribution.) You can see this
banding when viewing the clips in-camera. These are not overexposed.
Any ideas of what might be causing this? Can it be fixed with camera
settings, or does he just need to give me his EX-1 and get another
camera? ;-)

Thanks,

Paul Bean

Paul Bean
Joshua Tree Productions
Las Vegas, Nevada


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Clint Fleckenstein
Re: Banding when shooting lightning
on Sep 22, 2009 at 6:08:32 pm

That looks like a rolling shutter issue to me. I know there have been a lot of artifacts blamed on this, some correctly and some incorrectly, but this looks like a clear-cut case.

If I'm correct it's not a camera setting. It's inherent to a CMOS imager instead of a CCD. CCDs have their own issues, of course.

Cf


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Craig Seeman
Re: Banding when shooting lightning
on Sep 22, 2009 at 6:12:59 pm

Cameras are only as good as the person using them

Alistar Chapman is a storm chaser who shoots lots of lighting with the EX.
http://www.ingenioustv.co.uk/



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Michael Slowe
Re: Banding when shooting lightning
on Sep 22, 2009 at 7:46:02 pm

Was with him yesterday at a Sony camera day at Top-Teks (UK) and he is great. Didn't show any lightning though.

Michael Slowe


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Craig Seeman
Re: Banding when shooting lightning
on Sep 22, 2009 at 7:57:35 pm

I remember he posted somewhere else on the internet how he sets the camera to shoot lightning. I vaguely remember a slower shutter speed was important.



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Clint Fleckenstein
Re: Banding when shooting lightning
on Sep 22, 2009 at 9:31:08 pm

I've seen that kind of artifact before on my Canon DSLR (also a CMOS sensor) when I wasn't synced to the external strobes properly - ie, too fast of a shutter speed. So while an artifact of the sensor, I suppose a slower shutter speed would compensate for it. I wish I knew what I was talking about.

Cf


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Michael Slowe
Re: Banding when shooting lightning
on Sep 24, 2009 at 10:09:29 am

Craig, Alister has a web site for his 'Severe Weather Stock Footage' company called Ingenious TV and the site is http://www.ingenioustv.com there might be footage of lightning on that but it won't explain how they got it! Messing around with the shutter speeds must be part of the answer. There is certainly a problem with the CMOS chips and I've experienced banding where photo flashes were present at a shoot.

Michael Slowe


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Derek Reich
Re: Banding when shooting lightning
on Sep 23, 2009 at 2:40:30 pm

That definitely looks like a rolling shutter issue. I have seen that exact same banding not with lightning, but when a lot of flashes are going off in a press conference. (or even just one flash sometimes)

I hope you are able to work out a viable solution. I did notice some rather extreme interlacing artifacts though.... that does not seem normal even for rolling shutter issues. Maybe that's from your compression to the web site?



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John Cummings
Re: Banding when shooting lightning
on Sep 24, 2009 at 12:34:40 am

I don't know...looks like two issues.

Going frame by frame, I do see the "partial frames" that look like cmos rolling shutter...but the fine horizontal black lines look like something else to me...not sure what, though...maybe derek nailed that about the recompression for the web.

J Cummings
Cameralogic/Chicago
cameralogic.tv
HDX-900/HDW-730S/DXC-D50


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Alister Chapman
Re: Banding when shooting lightning
on Sep 24, 2009 at 7:15:40 pm

That looks like a really bad case of rolling shutter and interlace. The best way to combat rolling shutter is to use the slowest shutter speed you can get away with. Interlace is never ideal for lightning as you often end up with the lightning over just a single field which then leads to the fine lines you see. I always shoot lightning using progressive. 30P will be better than 60i, better still is 24P. At night I shoot using a 2 frame slow shutter.

By using a slow shutter you minimise the risk of the lightning occurring only during the CMOS scan cycle. The slower the shutter the longer the gaps between scan cycles.


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