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HPX500P - Digital noise in recorded image

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Matthew Gospodinovich
HPX500P - Digital noise in recorded image
on Sep 13, 2011 at 1:47:19 pm

Maybe digital noise isn't the word for it, but I've linked a picture so you can see it.

https://picasaweb.google.com/lh/photo/ZDXFnUuFQi-hOg421Bz_7A?feat=directlin...

We were getting footage of one of these indoor emergency strobe lights. Recording in 1080i/24PA mode with 180d shutter. We rolled some without the shutter too, because we were missing some of the flashes, obviously they only flash for a fraction of a second, and sometimes the camera doesn't see it at all.

The results were very dynamic. I probably should have posted more stills, but this one gives you the main idea. Some frames you would just get a white flash that fills the screen, which is what you would typically expect if your frame rate and shutter were all working with you and you caught the strobe at just the right point. Many if not most other frames contained some noise that looks similar to this image, a bright flash area usually green or purple, and a line that runs across the image. Sometimes across the top, sometimes across the bottom, sometimes only green, or only purple. Sometimes no line, just a green smudge.

So my guess is that the strobe is flashing pretty intensely through the optics and hitting the camera's sensor and kind of "overloading" it, i guess you could say. I figure is some point way past your typical "bloom" or "blown out" or "hot" levels, hence the weird noise stuff.

It kind of reminds me of what I figure tube camera burns looked like, though Im too young to have worked with tube cameras, i can imagine it was something similar.

To my knowledge, the camera is still recording fine, haven't noticed any problems since.

Any thoughts on what is happening here, or if we should be worried about damage to the sensor?


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Matthew Gospodinovich
Re: HPX500P - Digital noise in recorded image
on Sep 13, 2011 at 3:01:44 pm



Here is the picture- my link didn't work on the original post


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John Fishback
Re: HPX500P - Digital noise in recorded image
on Oct 3, 2011 at 8:18:30 pm

I agree it looks like an overload of some kind. Did you see this on your monitor while shooting? If you need to re-shoot, dial in the strongest ND and expose for the flash. Don't worry about the background. You might have to combine two shots - one exposed for the wall and non-flashing light and the second exposed for the flashing. This will be stopped down to the correct exposure, thereby, darkening everything but the flash. Then combine the shots using a luma key or a Composite Mode.

John

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