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Old January 31st, 2010, 01:41 PM   #1
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Location: Lincoln, NE
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HD-SDI live capture - Experiences? Settings?

I've been experimenting with the HD-SDI output on my HD250 capturing directly via a Blackmagic card. I have to say, I'm a little disappointed.

I was expecting less noise than HDV footage. I need to do some more testing, but my first impression is that the SDI footage is just as noisy as the HDV, well maybe a little less but not much. That makes me think it's CCD noise or I may need a totally different scene file recipe for SDI capture. I'm using the same tweaked version of Paolo Ciccone's True Color for the 250 that I use when shooting HDV. Or is it that my coax is too long? I'm testing with 15ft of cable.

Is anyone else doing this? What's been your experience? Are you using a special scene file recipe?
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Old February 1st, 2010, 06:28 AM   #2
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If you would compare Analog Component with HDV recording/SDI output you would see less or more noise between them.
HDV and HD-SDI are both digital, so the actual noise level from the CCD should show pretty much the same as there are no analog conversions in between. The only big difference between the HDV and SDI is that SDI is uncompressed video signal.
From my feeling because the camera compresses the signal on tape or FireWire, some degree of noise is compacted in HDV (showing black artifacts instead though)
HD-SDI is digital, so the length of the cable will not add more video-noise. It is the best available output you can get from the camera.
Marc Colemont - Belgium - http://www.mc-productions.be
JVC GY-HM850's, HM890, HM600
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Old February 1st, 2010, 10:32 AM   #3
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Thanks, Marc. I suppose my expectations were too high. It makes sense that the noise is CCD related. I was hoping the HDV compression was introducing more noise than it actually is.

The cable length was a grasp at straws to explain my disappointment. It didn't make sense that 15ft would introduce any issues. I've run 100ft of coax in other applications without a problem, but never from this camera.

Now I just need to decide if being tethered to a capture system for 10bit 4:2:2 with similar noise is worth the hassle. I'm shooting my second feature with this rig in April.

The first was shot to tape and transcoded to Cineform for post (included green screen composites and color grading) and I was quite pleased with the results after using Neat Video to clean up the noise.

I was hoping to eliminate a great portion of the Neat Video cleanup. It's time consuming. I can see a theoretical advantage to 10bit 4:2:2 transcoded to Cineform as compared to the 8bit 4:2:0 HDV transcoded. Theoretically I should have better information for the color grading and compositing processes, but is so much better that it's worth the hassle of a tethered camera?

That's what I need to test. I need to capture the same footage to tape and via HD SDI and process the crap out of it and see what happens.

Any thoughts or experiences would be greatly appreciated.
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