Blackmagic Forum

Hi there,

could you guys help me with the following problem:

I have ARRI raw footage and need to export to EXR (scene linear of course).

In Hiero this is very straightforward as EXR is always linear, but I am struggling in davinci.

Could someone be so kind to explain this step by step?
Raw settings are setup correctly (I assume) wide gamut, etc...

I assume the only thing I need is a lut to get rid/invert of the gamma, but I am not sure how to get it, where to apply at and how the export settings need to be.

Thank you,

Timor Kardum
VFX Supervisor
OMSTUDIOS Berlin

Hi Timor

In the config you can choose ACES colorspace and a Arri/Alexa IDT and no ODT.
Then it should work fine.

Regards, Jaap Kok

Hi Jaap,

Thank you for the swift reply, will try and let you know.

ACES sounds good, hope it works out.

Cheers,

Timor

Hi Jaap,

I didn´t succeed.

Could you maybe be a bit more specific on the steps i need to follow. The EXR that came out was extremely dark, didn´t quite look linear to me...

Bear in mind my knowledge of DaVinci is very limited.

Thanks again,

Timor

Hi Timor,

Unfortunately I don't have acces to a Resolve at this moment, which makes it a bit
difficult for me to explain it to you.
Maybe somebody else on the forum can help you out?

Regards, Jaap

why you do have to work in linear EXR? (It might not make sense at all)

Hi Walter,

there are many reasons one wants to work without a gamma applied. 80% of all VFX houses worldwide have this as a standard workflow and given the fact that it becomes standard in DI pretty soon (ACES) I think the advantages are obvious.
We have a show with 120+ VFX shots, mostly arri raw with a bit of prores and i want to make sure we have the best starting point, and that is scene linear.

The best paper i´ve found so far explaining the "why" is found here:

http://github.com/jeremyselan/cinematic ... or_VES.pdf

It´s a great read

Especially for VFX you want a format that is floating point and can hold values >1, and there are not many options/formats out there that can give you this (basically none other then EXR).

As I wrote earlier we can do this very easily with The Foundries Hiero, but on this show we had troubles conforming with it and more success with DaVinci.
I wanted to know how to export lin EXR from DaVinci since quite a while, unfortunately most colorist we work with are not VFX savvy and cannot tell you how this has to be done.

Regards,

Timor
omstudios Berlin

ok....

I think the best way is to create (in nuke for example) a very dense 1D LUT for [SLog to Linear] and [Linear to SLog] and use it as explicit IDT/ODT ( or as color space transformations.

(basic Idea can be found here: http://forums.thefoundry.co.uk/phpBB2/viewtopic.php?t=8284&sid=fab29d7d836ab84b2575172b8f28fca2 .. there is a thread where it explain how to build a 1D LUT in resolve. I think is 12 bits in, 16 bits out. So, you will use a different ramp that the one proposed (4096) so you will not interpolate.

1) create the ramp/reading with the Nuke [Slog to Linear] OCIO tool applied (and the reverse)
2) make the right formatting in XCell
3) load in resolve and use it.

Basic Idea is to know where your color-space will be translated: you can use the SLog tool from resolve, look with a SLog to [rec709/BTU1886] standard LUT from Arri, then applied the [SLog to Linear] LUT in export.

When the shot came back from VFX, you will use the 1D input LUT [Linear to SLog] (shot based) as first operandi of the shot itself that will bring back the shot in the SLog color space of the movie...

All easy right?

Hi Walter,

thanks for taking your time to write this, appreciated!

Will let you know how we manage.

Cheers

Timor

Haha Resolve did a better conform than Hiero? Amazing!