RCM Workflow - White Balancing in Log space

[Douglas Dutton]

Hi everyone!

I've been experimenting with RCM and Davinci Wide Gamut and really enjoy it so far!

However I like to do my White Balance adjustment using printer lights to the log space of the image.

When I work with Prores, RCM cannot detect which camera the footage has been shot on, so I can balance the footage in the log space.

However when I work from the Raw or the  native camera file, Davinci will convert the footage to Rec709  2.4 (set as my output color space).

And that seems to be how my footage is inputed in Resolve.

In RCM workflow, How do you balance your footage in the log space and not in an already converted space?

Many thanks

Douglas

[Samuel Holdridge]

Hey Douglas, 

I have also been working in Davinci wide gamut a lot myself lately and have been running into the same issue. I dont know if this will help but this has been my solution thus far, not sure if its entirely correct but I have had good results and more control over my images. I just keep my color space in rec709 and use a cst to convert my image into DWG so that i still have control over the log image since i find it comes in with something crushed from time to time. Like i said im not sure if this is right and if someone has a better workflow for DWG please respond LOL i would love some more perspectives

[Anton Meleshkevich]

RCM has a lot of bugs.
I think the best is to stay in DaVinci YRGB and to set timeline colorspace according to your source footage.
So for alexa source files you set timeline colorspace to Alexa LogC.
So HDR pallete works as it should. And Global now behaves like WB in RAW (Gain in linear LMS) or like chromatic adaptation plugin. And for mixed cameras I'd use Color Space Transform effect.

I use ACEScct timeline color space. And DCTL as IDT and ODT (it's works faster than ACES Transform effect). And global wheel behaves the same. The main reason why I use ACES is it's amazing gamut compressor (currently available as DCTL). I hope it will be included in Resolve out of the box with the release of ACES 1.3.

On 4/3/2021 at 10:57 AM, Douglas Dutton said:

Rec709  2.4

Your file should be rec709(-ish) with linear segment near black or any kind of similar tone-mapping. Not a pure gamma 2.4, which is a display gamma only. So you probably should use rec709 scene, not gamma 2.4. I guess gamma 2.4 was default until v17 for creating DCP, where, I believe, transformation goes from timeline color space (to p3 gamma 2.6). So probably this is why timeline default color space is display gamma, not the gamma of the video file.

Edited April 5, 2021 by Anton Meleshkevich

[Douglas Dutton]

@Samuel Holdridge Thank you Sam, that's interesting!

@Anton Meleshkevich Hi Anton and thanks for your detailed comment!

What you say about YRGB is interesting and if it's the only way to work on the footage in linear fashion then it's a no brainer...

I thought that in YRGB changing the timeline color space didn't change anything as when you do, your footage looks the same. Or does it?

And basically what I read about it is that if you want to change your export's gamma, you do need to add a CST Timeline node to convert it.

Thanks a lot for your input!

Douglas

[Jamie Neale]

@Douglas Dutton some of the tools are colour space aware so switching your timeline colour space helps that feature kick in.

RAW carries metadata to help resolve know how to translate to your working display colour space. If you're getting ProRes and don't have camera data/info, you could go back to the DP/Director and ask? do that all the time.

The non RCM route, using CSTs and manually controlling gamut/tone mapping is great for quickly testing out colour spaces to see which works best. One big difference is when using RCM you're also getting the use of Input/Output DRTs. You can get a similar result by doing this manually with the CST.  

[Douglas Dutton]

@Jamie Neale Thank you Jamie!

[Marc Wielage]

On 4/2/2021 at 9:57 PM, Douglas Dutton said:

When I work with Prores, RCM cannot detect which camera the footage has been shot on, so I can balance the footage in the log space. However when I work from the Raw or the  native camera file, Davinci will convert the footage to Rec709  2.4 (set as my output color space). And that seems to be how my footage is inputed in Resolve.

One thing you can do: highlight the clips, then right-click and select "Bypass Color Management." Then, using a Color Space Transform OFX plug-in, you can drop it into the first node and tell it what kind of camera made the ProRes file. I can't guarantee this will work every time, since it's possible when the ProRes was made, some kind of change or adjustment will happen, but it can work. Experiment with different settings and see if this gets you to a closer starting point.

I should acknowledge Joey D'Anna of MixingLight for coming up with this "Roll Your Own" color management idea, which I think is very clever. I hadn't used CST nodes until his suggestion, but they've proven to be very useful.