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Black levels on By-Ref and SelfContained clips

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Jack Shepard
Black levels on By-Ref and SelfContained clips
on Sep 10, 2008 at 5:19:28 pm


Great news on the FCP and Media 100!

Question: When I export a By-Reference clip or a Self Contained Clip it seems like my black levels seemed washed out. Any ideas why this is happening?


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Wickham Strub
Re: Black levels on By-Ref and SelfContained clips
on Sep 10, 2008 at 8:33:55 pm

Hey Jack,

•What codec(s) are you using?

•HD or SD?

•Anything else you can think of?

~Wick



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Jack Shepard
Re: Black levels on By-Ref and SelfContained clips
on Sep 10, 2008 at 9:43:50 pm


I was actually using the Media100i codec on this particular one. But I have noticed it on a project I did using the DVCProHD codec as well (though everything looks fine when I am going to tape). for this project, I was exporting a by-reference clip and then was going to make different compressions from that using quicktime. But the black level is off. So, for example, I brought a still file into Boris Fx and shrank it. But the black of the card isn't matching the background around it, if that makes sense. In contrast, when I export a non-compressed clip/animatic codec clip using quicktime the blacks export fine.

Any ideas? Thanks so much.


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Floh Peters
Re: Black levels on By-Ref and SelfContained clips
on Sep 10, 2008 at 10:24:27 pm

Jack,

you are running into the usual 0-255 vs 16-235 RGB luma level range. Media 100 i codec uses a 16-235 luma range when being converted to RGB via QuickTime, DVCPro does use 0-255. Both are perfectly legal ways of handling luma ranges, and both have advantages and disadvantages. One thing you should not do for a by-reference or self-contained export is to mix formats. If you mix formats for whatever reason in your timeline, make sure to use the QuickTime export to a codec of your choice, and choose your target range depending what you want to do with the resulting file. E.g. if you want to use the files in Compressor, use 0-255. If you e.g. want to use them in AE and render back into Media 100 i codec, use 16-235. Some apps (like BitVice for example) do support both luma ranges. In BitVice the 16-235 range is called "StudioRGB" vs. FullRGb for the 0-255 range.



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Jack Shepard
Re: Black levels on By-Ref and SelfContained clips
on Sep 10, 2008 at 10:35:58 pm


I see. I see. I have been working a lot with projects that have mixed media lately - maybe that's why I suddenly started noticing it. Thanks for the indepth answer.


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David Issko
Re: Black levels on By-Ref and SelfContained clips
on Sep 11, 2008 at 5:10:56 am

I came across this issue quite a few years ago when M100 did not offer a 16-235 or 0-255 range choice like it does now. I happily edited my project in M100, exported the files as a by reference, used QTPro to make my MPEG2 files for DVD and watched in disappointment when my wonderful program had a high setup, which I could not work out for some time.

Although it takes a painfully long time to export, I always use 0-255 range when making DVDs as I use Compressor for the MPEG2 files. If anyone knows what adjustments I can make on Compressor to suit a M100 by reference export, that would be great.

I know that Bitvice is probably a better way for me to go and I should update my very old version.

Best Wishes
David Issko



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Michael Slowe
Re: Black levels on By-Ref and SelfContained clips
on Sep 11, 2008 at 9:25:08 am

Even with BitVice I find that contrast (& black) is diluted somewhat and have lately taken to increasing contrast levels after I have done my tape master and before exporting by reference and using BitVice to encode the .Mov file.

Michael Slowe


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Jack Shepard
Re: Black levels on By-Ref and SelfContained clips
on Sep 11, 2008 at 11:48:07 am


Someone had posted this awhile ago and I jotted it down. Never really put my black/white setup issues and the DVD process together before. This has worked with me while making DVD's in Compressor:

NTSC
4:3
upperfield
closed gop
7 frame structure
Filters:
black restore + 7.5
colors (highlights and midtones = +20 (leave shadows/lowlights at 0 or you add noise back to your blacks)
Gamma is 1.4 (you could try 1.3 and 1.5)


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