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Sony HVR-A1 and HDR-HC Series
Sony's latest single-CMOS additions to their HDV camcorder line.


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Old August 14th, 2005, 02:15 PM   #1
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Flashes from cameras causing problems in HDV?

I shot some video with my HC1 of some models getting their photos taken and after each flash there were several frames that had very bad blocky artifacts.

I have shot similar footage with an FX1 and never have seen such problems.

Anyone have similar problems?
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Old August 14th, 2005, 02:49 PM   #2
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Thanks for posting this, Greg. My first reaction is that it's perhaps due to an MPEG encoding problem, but strange that it would happen with one HDV camcorder and not the other. I think you've just created the basis for a very interesting side-by-side test!
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Old August 14th, 2005, 03:13 PM   #3
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CMOS devices(HC1)use rolling shutter charge/readout architectures. A flash causes local strong frame content change which fools the MPEG encoding.
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Old August 23rd, 2005, 12:44 AM   #4
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Quite common actually?

Quote:
Originally Posted by Greg Jacobson
I shot some video with my HC1 of some models getting their photos taken and after each flash there were several frames that had very bad blocky artifacts.

I have shot similar footage with an FX1 and never have seen such problems.

Anyone have similar problems?
I've seen this on several HD broadcasts. Example is the HDnet program where they video folks on the red carpet. If it is in an exclosed place and you have lots of flash's going off...the picture will disolve into a blocky mess as the flash's pop.

Also seen this on Leno with strobing lights. Same effect.
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Old August 23rd, 2005, 04:04 AM   #5
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Quote:
Originally Posted by Thomas Estrella
I've seen this on several HD broadcasts. Example is the HDnet program where they video folks on the red carpet. If it is in an exclosed place and you have lots of flash's going off...the picture will disolve into a blocky mess as the flash's pop.

Also seen this on Leno with strobing lights. Same effect.
Did you see this on different HDTV brands? Some decompressors can handle pathalogic mpeg2 signals better than others.
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Old August 23rd, 2005, 11:35 AM   #6
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This has nothing to do with decrompressors. Like previously stated, it is indeed the rolling shutter effect. You can see similar artifacts with fireworks. Unfortunately, this is a problem with the CMOS sensor and HDV. So no other HDV camcorder will produce this problem; only the HC1. I have been asking DSE if the A1U reproduced such problems and he was not able to answer. I guess we need to wait and see. I predict that you will get similar problems as it uses the same chip.
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Old August 23rd, 2005, 01:29 PM   #7
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I filmed the Butthole Surfers in 2002 and the strobe lights were incredibly hard to compress to MPEG2 without blocks. I can't even begin to imagine a realtime encoder doing any better.
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Old August 23rd, 2005, 03:00 PM   #8
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[QUOTE=Greg Jacobson]I shot some video with my HC1 of some models getting their photos taken and after each flash there were several frames that had very bad blocky artifacts.

Alexander, several frames are contaminated. Could you explain, if the (long GOP) MPEG2 codec is not involved, how a rolling shutter could affect "several frames" while an electronic flash lights up during only less than a few % of a frametime
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Old August 23rd, 2005, 03:28 PM   #9
 
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Quote:
Originally Posted by Alexander Karol
This has nothing to do with decrompressors. Like previously stated, it is indeed the rolling shutter effect. You can see similar artifacts with fireworks. Unfortunately, this is a problem with the CMOS sensor and HDV. So no other HDV camcorder will produce this problem; only the HC1. I have been asking DSE if the A1U reproduced such problems and he was not able to answer. I guess we need to wait and see. I predict that you will get similar problems as it uses the same chip.
Alexander, I answered you as best I could. I shot the camera with a pan going from a dark surface to a bright light back to a dark surface and didn't see this. That was the best test I could do in the time that I had the camera. It's also important to note that I was dealing with a prototype. the "real" ones will be shipping off the lines shortly.Then others will be able to test.
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