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Black level for DVCProHD?
We just shot some footage using a brand new HDX-900 (DVCProHD footage)and I brought it in to FCP over Firewire. I looked at the footage using an external scope (over HD-SDI), and it looks like the blackest part of the image is coming in at 7.5.
I was under the impression (a dangerous way to start a sentance, I know) that since DVCProHD is a digital signal, coming in through firewire into FCP, that my black level should be at 0. Since I am using LCD monitors over HD-SDI for monitoring, I should keep my black at 0. When I lay off to Betacam (or any other analog format) I whould then add setup to the signal so that my black is 7.5.
Is this a correct workflow? If it is, do I need to setup the camera to put blacks at 0? If I capture over HD-SDI instead of firewire, does black stay at 0?
I should add I am using a Kona 2 card for output, using DVCProHD 720p30 footage.
I did a quick Google search before posting and I think I’m right, but if you know of any links that go into this in more depth, please share.
Thanks-
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6 Replies
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[Matt Larson] “I was under the impression (a dangerous way to start a sentance, I know) that since DVCProHD is a digital signal, coming in through firewire into FCP, that my black level should be at 0. Since I am using LCD monitors over HD-SDI for monitoring, I should keep my black at 0. When I lay off to Betacam (or any other analog format) I whould then add setup to the signal so that my black is 7.5.”
Yep, it should be 0 on the blacks, however the camera operator can set up the camera however they choose. So if they shot with the blacks high, then that is what you will see. So then you color correct to get the blacks where you want them.
I run my blacks between 0 and 5 depending on how I want the final color correction to look.
Walter Biscardi, Jr.
https://www.biscardicreative.com
HD Editorial & Animation for Food Network’s “Good Eats”
HD Editorial for “Assignment Earth”“I reject your reality and substitute my own!” – Adam Savage, Mythbusters
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Matt,
In addition to what Walter said, keep in mind that most cameras are setup to record blacks at 7.5 because it gives you the most latitude in post. While you can crush the blacks in the camera, if you decide later to uncrush them in post, you will most likely add anomalys to your otherwise pristine video.
DRW
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[Matt Larson] ” If it is, do I need to setup the camera to put blacks at 0? If I capture over HD-SDI instead of firewire, does black stay at 0?”
Only Analog signals need setup for SD and NEVER for HD.
Over HDSDI it should always be at 0.gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows -
Setting a digital video camera to incorrectly record black at 7.5 IRE will give less digital levels for the recording – about 7% less.
Setup has nothing to do with crushing blacks. It’s a bias in the analogue recording realm to deal with TV flyback issues that are long gone.
Now some cameras may implement it all wrong and give anomalous results that could be percieved as having more lattitude, but that’d be bonkers. Digital was designed to always record at code 16, which is not the case if you burn in a setup into the digital signal. It should read 0% in FCP’s scopes.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
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Graeme,
I’m not disputing you for a second, you know an awful lot about this stuff for sure, and I’m only repeating what I was told by the engineer I asked last asked about this puzzle. So, please do explain, why is the default on most, if not all, digital cameras set at 7.5, making it necessary for those of us in post to invariably bring black levels down to 0? Inquiring minds want to know…
THNX,
DRW -
First, there are two kinds of digital cameras: ones that do it “right” and ones that do it “wrong”. Ones that do it right, will, if asked add 7.5IRE setup to the analogue outputs only, and when recording, correctly place digital black at code 16. Ones that do it wrong, fake black to be 7.5IRE on analogue by adding ~16 code values to black on the digital, recording black around code 32, wasting 16 code values, and making the digital tape somewhat incompatible with anything else.
I’ve not, personally, seen cameras default to 7.5IRE setup. Most “prosumer” level cameras default to how they’re made in Japan for the Japanese market where setup is not used.
Another thing is that with HD, there is no 7.5IRE setup in HD at all. It’s not in digital and it’s doubly not in Digital HD.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
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