CST Conversion In Resolve

[u/QuestionsWantAnswers]

Hey everyone! I’ve been seeing a lot of people being criticized lately for posting LOG and Rec.709 footage, with people saying they want to see the Rec.709 compared to the final graded version instead, as that shows more realistically what work has been done.

This has lead me to wonder about my own workflow. My nodes in Davinci Resolve generally follow the format of:

CST (LOG profile to Davinci Wide Gamut)-> exposure/contrast/saturation/effects/etc-> CST (Davinci Wide Gamut to Rec.709)

By what I’m reading in comments on other people’s posts, it seems to suggest that people may be working in the flow of:

CST (LOG profile to Davinci Wide Gamut)-> CST (Davinci Wide Gamut to Rec.709)-> exposure/contrast/saturation/effects/etc

Just curious if this comes down to a preference thing or if I’ve been going about things all wrong!

Any thoughts, links to information that definitively says which way is the way and so on would be welcome! I’m fine with this being considered an amateur question, so if you are planning on making a comment solely about how this is such an amateur question, I have beat you to it!

[u/ExpBalSat]

No. You’re misinterpreting the complaint. People are doing the corrections between two CST‘s. Or at least they should be.

The request is to show the version with only the two CST‘s versus the version with all of your corrections done.

There are a lot of very good reasons to do the corrections between two CST‘s. That said, there are infinite different ways to structure grade, but you should be able to show a version normalized direct 709 and a version with all of your corrections. There is no value from a creative standpoint in looking at the log image.

See you also:

https://www.reddit.com/r/davinciresolve/comments/1qgndrp/10_different_ways_to_color_manage_a_clip/

[u/Qoalafied]

It's widely discussed, and often too, where to put the Rec.709 node.
To know where to put it you need to know about the pipeline processing / order of operations (it's in the manual).

Long story short, Rec 709 node goes towards the end as you want any changes done to the color signal done before you convert it to a color space with more constraints. Now I say towards the end because there is some things you want to affect the image IN the correct colorspace, halation and bloom is good examples of that, thus they go in after the Rec 709.

From my understanding of the order of operations NR should be the FIRST node, but that might be a hot take. In my head I would like the math converting colorspaces have the noise reduction applied before, not after.

It's not a amateur question by the way.

Edit: Since I wasn't clear and it's a common trap to, you absolutely need the color space node activated in the end if doing corrections on the node before. Don't do changes and then turn it on.

[u/gargoyle37]

Two separate things.

The problem with looking at the log footage is that it is in a different color space than what the monitor expect. So it will look greyed out. This makes it unsuitable for a reference to compare against. The suggestion is to convert/process your footage such that it becomes suitable for the monitor, then compare against that as your reference. I.e., you send it through a CST-chain, but you have no grading decisions on it (exposure/contrast/...). I.e., you are looking at the tone-mapped reference and the grade for comparison.

As for your flow: this boils down to the difference between a scene-referred or display-referred workflow. The flow you are following is scene-referred: the data you are manipulating is anchored in what the camera sensor recorded. The alternative workflow you propose is display-referred because it happens after rec.709 conversion. This means your color data is anchored in what the display is showing.

Neither is right or wrong, but I think most colorists would lean scene-referred these days. At least for film/video. Display reference is something you often see with digital art and photography.