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Sony Slog to DNX185X

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Dan Davis
Sony Slog to DNX185X
on Jul 30, 2016 at 1:45:07 am

Hi all,

Just a quick question....

I've just received a 10bit dnx file (one long clip) exported from media composer to grade, originally shot slog.
For various reasons that I won't go into I'm not getting the original camera files. As far as I know all the slog footage was
ama linked and then transcoded to the 10bit codec. How much in a real world situation am I losing (for the grade) range wise using the mxf file as opposed to the camera files. I may be wrong but I would have thought that the 10bit file would retain any information.

Thanks for any help.
Dan



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Joseph Owens
Re: Sony Slog to DNX185X
on Jul 30, 2016 at 3:56:04 pm

[Dan Davis] " I would have thought that the 10bit file would retain any information."

A matter of some curiosity to myself as well. There are some compromises in this approach IMO, because I am not convinced that the "ranging" and gamma-transfer curves are equally valid for both data formats. Bringing in DnX-"baked" MXF containers does not yield the same output values in Resolve that are being generated in NLE applications using their versions of, for example, any of the Sony S-Log profiles. This is easily tested by comparing a baked offline chase video with a side-by-side grade in the color correction timeline. The disparities that I see can be somewhat matched by cascading a number of profiles -- using two successive OFX ColorManagement nodes can come close -- experimentally I can recreate more or less the same Media Composer output with a "Rec-709" concatenated with a "SonySlog" gamma transfer, but this is still two nodes before I can start where the editor left off. If there is a fairly large exposure-delta, the anti-log transform still might be distorting the transfer curve to a point where I may as well have re-engineered my own linearization process - and for which the camera originals may have the best chance of success.

Bottom line, though, is if you are in the middle, not really any differences to speak of, but if the shot needs to be pushed or pulled some distance, worth it to reconform.

jPo

"I always pass on free advice -- its never of any use to me" Oscar Wilde.


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Dan Davis
Re: Sony Slog to DNX185X
on Jul 30, 2016 at 8:13:22 pm

First of all I want to thank you for your reply, very helpful!

News update:
I started grading the programme today as if I was working with the original slog camera files, no luts involved and happy with where it's going. I get a call telling me that there is a drive with some (not all) original log footage. Because I can't get all the files I carry on but ask them to send drive over anyway. To cut this story short...I brought into Resolve an slog shot that has been used. Stuck it on layer 2 and applied the exact same grade (5 nodes) and toggled between layers, MXF DNX185X and slog3. To my very keen eyes and indeed the external scopes there is nothing between them, not even a nats movement on the scopes. All very interesting!

Thanks again.
Dan



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