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Uncompressed 10-Bit Gamma Shift

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Adam White
Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 4:01:04 pm

The short film I'm producing is currently being color graded at a post-production house.

I need to pull the graded film back into Final Cut Pro for audio mastering e.t.c. They can only provide a 10-bit uncompressed QuickTime as final output, but have advised there will be a slight gamma shift with this export format.

My question is - how much of a shift will occur, and what steps can I take to remedy this on my end? I'm also going to need to convert the uncompressed file into a ProRes format as my machine won't be able to adequately edit an uncompressed file (I'm not on a high-end setup!) - how much of an issue will this prove?

We are on a shoestring budget and we've had compromise the whole way through our production. Appreciate that this is less than ideal, but what do you experts suggest as best way to fix gamma shift?

Best,
Adam


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Chris Borjis
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 5:14:16 pm

3 way CC and look at it on the scopes. maybe it just needs to have the blacks lowered a little.
export that as ProRes.

sounds like they may have been grading with after effects?




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Jeremy Garchow
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 5:37:15 pm

[Adam White] "but have advised there will be a slight gamma shift with this export format. "

What are they grading on?


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Adam White
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 6:14:55 pm

Hey Jeremy - thanks for response.

They are grading on latest version of Blackmagic DaVinci Resolve.

Adam


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Jeremy Garchow
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 6:19:06 pm

What would they rather give you so there's no shift?

Unless they are talking RGB to YUV


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Adam White
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 6:26:51 pm

The only other option is ProRes 4:2:2 or 4:4:4. But this is a more problematic for them - I should add that this has been done for us as for free after I called in some favours and so we aren't in a position to ask for more resources and/or time in all honesty.

It's looking like Uncompressed 10-Bit is the only practical option for us at this stage (and we need this completed ASAP) so that in mind, what should I do to the file on my end with either Final Cut Pro or Color to resolve this gamma shift issue?


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cowcowcowcowcow
Jeremy Garchow
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 6:33:19 pm

I would say probably nothing. Take a look at the footage and see. I'd have them render out a grey scale/color bars you have sent them through their system, and you'll be able to see what is going on a bit better. I can't imagine it will be a huge shift.


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Adam White
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 6:41:32 pm

Jeremy - many thanks for your input!

I thought myself that the shift would be negligible but wasn't too sure. If I can I'll definitely have them render out a gray scale/color bars - a great suggestion!

Which flavour of Apple ProRes do you suggest I convert the Uncompressed 10-Bit QT to? And are there any color/gamma settings I need to be aware of when converting the file?

Thanks for all your help,
Adam


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cowcowcowcowcow
Jeremy Garchow
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 6:44:48 pm

ProRes HQ

[Adam White] "And are there any color/gamma settings I need to be aware of when converting the file? "

Use Compressor and turn frame controls on. In the video codec tab, make sure to set the gamma correction to none from automatic.

Jeremy


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Adam White
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 8:09:36 pm

Great.

Just a couple last questions about specific settings;

- Enable chroma filtering for 4:4:4 sources?
- Output Color Space: Default for Encoder or Preserve Source?

And lastly, I assume all three variables in resizing and retiming controls need to be set to "Best"?

Adam


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cowcowcowcowcow
Jeremy Garchow
Re: Uncompressed 10-Bit Gamma Shift
on Nov 4, 2009 at 8:18:56 pm

[Adam White] "- Enable chroma filtering for 4:4:4 sources? "

No.

[Adam White] "- Output Color Space: Default for Encoder or Preserve Source? "

Preserve Source which should be rec 709.


[Adam White] "And lastly, I assume all three variables in resizing and retiming controls need to be set to "Best"? "

No, they don't. They can all be left to fast, but turning the frame controls on ensures a 10bit conversion.

Jeremy


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Neil Sadwelkar
Re: Uncompressed 10-Bit Gamma Shift
on Nov 5, 2009 at 2:35:08 pm

We output from a DaVinci Resolve as Uncompressed Quicktime. These are large movies and not like the Uncompressed 10-bit movies that FCP and Quicktime.

In Quicktime player, the movie properties look like this...
screenshot2009-11-05at7.58.37pm.png

By default, this is a 'log' quicktime which needs to be linearized. We usually do it in Shake with the Truelight node set for the correct film stock.

Or else it can also be linearized by the post facility. In that case the colours will be correct. We make these kind of quicktimes and then convert them to ProRes in an FCP system. We've seen no significant shifts in gamma or colour.

-----------------------------------
Neil Sadwelkar
neilsadwelkar.blogspot.com
twitter: fcpguru
FCP Editor, Edit systems consultant
Mumbai India


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Adam White
Re: Uncompressed 10-Bit Gamma Shift
on Nov 5, 2009 at 2:49:35 pm

Hi Neil, thanks for your reply.

I'll ask the post-production house about this, but if they can't linearize the uncompressed QT for me, can I do this myself? I'm assuming this is an essential step, and am I correcting in thinking that if this isn't done then I won't be able to convert the QT into a functioning ProRes file?

I have Final Cut Studio 3, and I know Shake is included though I've never used it before. We shot on HDV1080i60. What settings do I need to apply to the file in Shake, and are there any tutorials online? I've run a search but couldn't find anything though this is all new to me so in reality I'm not really sure what I'm looking for.

I would guess that we'll probably have to linearize the file ourselves, so would greatly appreciate any advice.

Thanks,
Adam


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Rafael Amador
Re: Uncompressed 10-Bit Gamma Shift
on Nov 5, 2009 at 3:48:30 pm

Here you have something to start with logarithmic files:

http://magazine.creativecow.net/article/cineon-files-what-they-are-and-how-...

In the Shake's manual there is interesting info too.
BTW, Shake doesn't comes in FCS and I don't think Apple still selling it.

rafael

http://www.nagavideo.com


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Neil Sadwelkar
Re: Uncompressed 10-Bit Gamma Shift
on Nov 6, 2009 at 5:11:56 am

Shake is not part of FCS and if you don't have it you can't buy it any more.

The Resolve facility will need to linearize for you with their LUT so they can confirm it with their calibrated monitors.

If they cannot/do not, and you don't have shake, I will need to check if Color can do the log-lin conversion on a Quicktime that's in log space. Incidentally, color can definitely do log-lin and rather good conversion, but on DPX or Cineon files.

Another utility that does a good log-lin and even provides controls for tweaking this, is Pomfort Cinemator.

The conversion from Resolve uncompressed Quicktime to Apple ProRes will be handled by compressor, or Color.

-----------------------------------
Neil Sadwelkar
neilsadwelkar.blogspot.com
twitter: fcpguru
FCP Editor, Edit systems consultant
Mumbai India


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Beverly Maguire
Uncompressed 10-Bit to DPX - Gamma Shift
on Mar 23, 2011 at 11:11:06 am

I get uncompressed Blackmagic 10 Bit, 1920 x 1080, Quicktimes from My Compositors. When I am finished with the Edit I need to Deliver DPX's to the graders.
I exported a Quicktime AJA 10-bit RGB Codec, 1920 x 1080, and Converted it to DPX using the AJA to DPX converter.

But when I check the DXP the Gamma has shifted.

It wont convert Uncompressed 10 Bit Quicktimes, it says it has to be RGB so Im thinking its the AJA that's changing the colour.

Please Help How can I export an Uncompressed Quick time (So to have no colour change) To DPX's for the Grading process.

Bev


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