Baselight, ACES, BLG and Nuke/Flame

[Nikola Stefanovic]

Hello,

I'm looking for some clarification, real world examples and best practice of using BLG workflow (in ACES) between BL, Flame and Nuke. Lets say if you have project shot with one camera things are pretty straight forward. Fun starts when you have timeline with Alexa mov, mxf and Arri Raw, few Red shots, little bit of Phantom Cine (that can not be loaded in Flame it seams) and few other exotic cameras and of course shots from CGI. I'm curious how other people tackle this problem. Especially from the Nuke side, since options in BLG for Flame are quite clear. What would be the best way to prep this kind of project?

Thanks,

Nikola

[Andy Minuth]

Hi Nikola,

you would definitely render everything into an OpenEXR with a Linear colour space. The colour primaries of this space depend on your workflow (709, AP0, AP1, E-Gamut, etc.). During this render In BL you have the option to smoothly bend in out of gamut colours, which might cause problems while comping or grading down the line because of negative code values. Use a slight CompressGamut for that.

Then you need BLGs for the full look or at least the correct viewing transform for the content to look right. You can export the viewing transforms as LUTs out of Baselight. Let me know if you need help with that.

Cheers, Andy

[Margus Voll]

Nuke can work very well with ACES just you need to know what you are giving out as plate it seems. Now i do not know what BLG gives forward in that regard as this might be the issue point. I work still in another app and there we have issue over that specifially as export and import spaces are different and it is not documented.

I do feature now and we have mapped what my app gives out and what it expects back and it seems to work fine just the question is when plates leave your app and what the BLG assumes it sits on. Like Andy already pointed with linear (709, AP0, AP1, E-Gamut, etc.) the same goes with ACES imo you need to know wahat you are passing on and what you are expecting back.

With VFX it is also good idea to keep whip in your hand if no color scientist at hand as usually VFX guys ask linear files but disregard 709, AP0, AP1, E-Gamut side totally as if they do not care. Mess comes out later. Sometimes Nuke users just do not know much about color management as well.

 

[Nikola Stefanovic]

 

15 hours ago, Andy Minuth said:

Hi Nikola,

you would definitely render everything into an OpenEXR with a Linear colour space. The colour primaries of this space depend on your workflow (709, AP0, AP1, E-Gamut, etc.). During this render In BL you have the option to smoothly bend in out of gamut colours, which might cause problems while comping or grading down the line because of negative code values. Use a slight CompressGamut for that.

Then you need BLGs for the full look or at least the correct viewing transform for the content to look right. You can export the viewing transforms as LUTs out of Baselight. Let me know if you need help with that.

Cheers, Andy

Hi Andy, thank you for answering.

Can we break it down more detailed?

So, if I understand you correctly, from the Baselight side:

- I should use ACES preset for BL project

- my working color space should be ASCEcct/AP1

- my DRT should be set to Truelight CAM or ACES RRT 1.0.1?

- mastering color space set to automatic from DRT or to something else like REC 709 in case of TVC workflow?

- set the correct (or use automatic) interpretation for different camera footage

- during the grading add Compress Gamut to avoid negative values?

- render Open EXR in linear color space, using stack color space, rendering flat pass?

- export BLGs

- pass flat pass and BLGs to Flame and Nuke

Please feel free to modify/adjust

 

Edited December 8, 2018 by Nikola Stefanovic

[Andy Minuth]

Hi Nikola,

I recommend to use the ACES or Filmlight template.

For ACES use ACEScct/AP1 as working colour space and RRT 1.0.1 as DRT.

For Filmlight use T-Log/E-Gamut as working colour space and TruelightCAM as DRT. TCAM is a very flexible solution and does not restrict you to a certain look. If you are not happy with the look of the TruelightCAM DRT, you can adjust it with the scene-looks in the Look tool. Add it as a bottom layer for example. If the blacks are too strong, raise the Flare parameter in a BaseGrade.

- always set the correct (or use automatic) interpretation of the footage

- optional: add a slight compress gamut in the grade to avoid negative values. This depends on the footage, and if the vfx department has trouble dealing with them. If you use it, I recommend to render it in the EXRs and bypass it for the BLGs. The idea is to fix problems with the footage that might occur while comping. 

- optional: do a tech grade of the shots, adjusting only the Balance ring (Exposure), trackball (Whitebalance) and Flare (black point). These operations maintain the scene-linearity and will not harm the image. If CGI elements need to be inserted and the plates are not matching, it might be difficult to match it later. Usually it is easier, when the shots in a vfx sequence are technically balanced. 

- render OpenEXR without grading (but maybe with CompressGamut and tech grade). For ACES the official recommendation is to use Linear / AP0. Some people use Linear / AP1, because certain VFX people prefer that. For the Filmlight worflow the recommendation is Linear / E-Gamut.

- export grades as BLGs

- On the VFX side, the people can choose the input colour space for the BLGs. They need to set this to the colour space that you rendered the shots to. Linear / AP0, Linear / E-Gamut, etc.

- VFX can use the BLGs to preview the look, and if the material is not coming back to the Baselight, they can even render the grades for the final output. But this must be tested and verified with Rec.1886 dpx files out of Baselight as a reference.

- If the material is coming back to the Baselight, they should not render the BLGs into the files. They will just render to the same Linear colour space as they got. 

- In BL import the finished VFX shots and verify/set the input colour space correct. The shots should match in colour.

Does that make sense?

[Nikola Stefanovic]

Thanks again Andy!

All that make sense and is very similar to my understanding.

I've tested BLG ACES workflow today with colleagues and while Flame side was pretty straight forward and successful, Nuke was giving us very hard time. We also had negative color values issue, but I already know how to deal with it.

Basically, for the test that worked on Flame we were using AP0/2065-1 as input and output color space for BLG plugin, running Flame in ACES color template, all smooth, matching with reference DPX 99,6%

In Nuke we tried all the possible combinations but no luck. We had success using so called 'telecine' script preset in Nuke and that works fine, but ACES nope. Maybe I'm missing something. Also Nuke color management is far from artist friendly.

[Margus Voll]

Ocio in Nuke.

[Nikola Stefanovic]

Yeah, I had that feeling also. We will try with OCIO color management tomorrow. Hope that will change something.

[Margus Voll]

I have feature now from Resolve to nuke and back over aces and ocio on nuke side.
Seems to line up perfect.