Timeline Working Luminance

Just looking at the new colour management in v17 and I'm stumped. Can anyone tell me what 'timeline working luminance' means? I've read the manual, and I'm afraid it makes no sense to me. To explain a bit further, I'm trying to use the colour management just for the input colourspaces - I'll apply my own output LUT and skip the output DRT completely. So, I select colour managed, my input, timeline & output colourspaces all as LogC and the output DRT set to 'none.' This setup should be the same (as far as I can tell) as having no colour management at all, but the 'timeline working luminance' gives different results. Why is this? Besides, what does timeline working luminance even mean in this case; I'd say the timeline is set to LogC, but that's a scene-referred colourspace, and I can only enter nit values which obviously relate to a display. Any ideas?

Oh, and to explain why I want to do this (and I did it in v16 all the time), there are a few reasons: First of all, I want to make the most of the colour management, but have a pool of output LUTs that I want to use instead of the 'DaVinci' output DRT option. Ideally blackmagic would allow us to create our own custom output DRT options, but they don't (yet). Until they do, this is the best I can think to do. Also, if I want to use colourspace aware grading tools like the HDR palette, then resolve needs to know the input / timeline colourspace. Presumably with colour management off entirely, these tools won't give the correct results.

Thanks

Just tried setting output colourspace to ‘bypass’ but the timeline working luminance drop down still impacts the result. Is there a way of turning it off?
To be clear, input colourspace is LogC, timeline colourspace is LogC and output colourspace is set to bypass. To my mind, no transforms should be applied anywhere. Why does the this option do anything in this scenario?

Just looking at the new colour management in v17 and I'm stumped.

That's why I prefer ACES. Easier to understand, less work, better results.

Correct me if I'm wrong but AFAIK it determines the operating luminance range for your tools.
If you look at what data is coming in to the HDR wheels at the bottom you can see that it's being compressed to 0-100 nits.

DRT DaVinci.png (566.43 KiB) Viewed 5018 times

By upping it to HDR 4000 you can see that it's mapping the incoming camera data to this range instead resulting in "more close to linear capture" working ranges.
This doesn't and shouldn't change the look of the output at all as long as you haven't made any color descisions yet.

It just gives you more granular control to use your tools, presumably also resulting in less work when having to output an HDR version after an SDR one or vice versa. Although I don't have any experience with HDR but I'm pretty sure it is designed with this in mind.

Where it "breaks" is when you choose something that is not DaVinci as Output DRT like IPP2, Simple or None.
The incoming data remains the same but you visually see the difference in data interpetation as it's not being converted to display space with the DaVinci system.

DRT simple.png (993.97 KiB) Viewed 5018 times

That's why I prefer ACES. Easier to understand, less work, better results.

Working in ACES doesn't have this "problem" because it's working in linear so as soon as data enters the interpretation doesn't change all the way till the output transform. So yea much easier to understand.

To jump back to the original topic. If your plan is not to use a managed workflow for multi display delivery or usage of mixed camera sources maybe not working in managed at all is a better choice if you'll apply your own LUTs because I assume the LUTs are based on a rec.709 source. If you don't manage anything you will see your Arri Log material just as log viewed on 709.

PRO TIP: In non-managed you can still utilize the extended luminance range of your footage with your HDR wheels if you change the gamma to the camera's encoding.

None-managed-workflow.png (386.38 KiB) Viewed 5018 times

[Rohit Gupta]

Just looking at the new colour management in v17 and I'm stumped. Can anyone tell me what 'timeline working luminance' means? I've read the manual, and I'm afraid it makes no sense to me. To explain a bit further, I'm trying to use the colour management just for the input colourspaces - I'll apply my own output LUT and skip the output DRT completely. So, I select colour managed, my input, timeline & output colourspaces all as LogC and the output DRT set to 'none.' This setup should be the same (as far as I can tell) as having no colour management at all, but the 'timeline working luminance' gives different results. Why is this? Besides, what does timeline working luminance even mean in this case; I'd say the timeline is set to LogC, but that's a scene-referred colourspace, and I can only enter nit values which obviously relate to a display. Any ideas?

Oh, and to explain why I want to do this (and I did it in v16 all the time), there are a few reasons: First of all, I want to make the most of the colour management, but have a pool of output LUTs that I want to use instead of the 'DaVinci' output DRT option. Ideally blackmagic would allow us to create our own custom output DRT options, but they don't (yet). Until they do, this is the best I can think to do. Also, if I want to use colourspace aware grading tools like the HDR palette, then resolve needs to know the input / timeline colourspace. Presumably with colour management off entirely, these tools won't give the correct results.

Thanks

You can set the timeline luminance to Custom and 5500 nits. Alternatively, you can disable the Input DRT, but it sounds like you do want the input side colourspace mapping.

You can set the timeline luminance to Custom and 5500 nits. Alternatively, you can disable the Input DRT, but it sounds like you do want the input side colourspace mapping.

Could you explain why it would have to be Custom 5500nits?

Thanks for the reply Rohit. I have some questions.

-Why 5500 nits?
-Is that specifically when working in LogC (i.e. with LogC as the timeline colour space)?
-If so, then do we need to enter different nit values for other colour spaces and are they documented anywhere?
-You suggested disabling the input DRT, but why would an input DRT do anything at all when the source and the timeline colourspace match?
-Can you please allow an option to disable this?

I feel that this 'timeline working luminance' may well have a use in certain cases, but there should be an option to disable it completely. Also, I feel the naming of this is misleading at best. I consider that the 'timeline colour space' (i.e. the uniform working colour space that all footage is transformed into before grading is applied) shouldn't have a luminance value that can be altered. As soon as you adjust the luminance values within LogC for example, it's not LogC any more. Even if you did want to adjust this for some purpose, why are the values given in nits, as this relates to display-referred images, not scene-referred (such as working in LogC).
Looking forward to your thoughts here, as I'm reluctant to use v17 on any projects until this is addressed or I understand the approach better.
Thanks
Chris

Hey Chris,

Have you've gone through my post already?
You might understand it a bit better then.

-Why 5500 nits?
Been asking that same question but after some testing I can see that after 4000nits the data from my arri capture doesn't change anymore so it could be above the camera's dynamic range.

-Can you please allow an option to disable this?
You can already disable it by setting it to 'none'.

I also tested disabling the Input DRT and it seems that this will disengage the timeline working luminance but keeps the management part of being able to pick Input Color Spaces for your footage and they get converted to chosen timeline colorspace in the background.
I was unaware of this in my previous post.

Again I think what you want to do is just have the system convert everything into Arri Log C and use the HDR tools with proper ranges. If you look at the bottom of my first post you'll see that you can even do this without using RCM on a non-managed rec.709 timeline.
All your non Arri footage could be converted with ColorSpaceTransform to that space or even with ACES transforms as effects on the clips at the edit page or through nodes.
Unless you have a logical reason to use Arri Log C as an output space but given the fact that you say you want to use LUTs I assume you want to transform to 709 or other display at the end of the pipe anyway.

Matter of preference at that point I guess.

Shebbe

Hi Shebbe,
Thanks for your detailed posts, and apologies for not replying sooner.
When I asked 'can you allow an option to disable this?' I was actually referring to the Timeline Working Luminance option.
Your screenshots are helpful, but they all feature the output colourspace set to rec709. In the example I'm talking about, I want to apply my own output LUT, so leave this set to LogC. I also don't do any grading operations, yet the highlights in the image change when I select different working luminance options. This makes no sense to me because I would expect the image to pass through unaffected.
The discovery you made about setting the input DRT to 'none' is great, as it seems to suggest that the timeline working luminance is tied to the DaVinci Input DRT. I will go ahead with this set to none as it basically does what I'm looking for and allows for the other benefits of colour management to remain. Thanks.
Just to delve into this a little further though, the idea of different input DRT options runs counter to my understanding of how this should work. In my example of LogC in and LogC out, there is no conversion (or certainly shouldn't be), so no input DRT should be applied. Besides, DRT stand for 'display rendering transform', and in this case we're not going to a display space, but staying scene referred. On top of that, even if my input was say SLog3, there is only one correct conversion to LogC from SLog3, so why would there be options here at all? Options for the output DRT make sense, as the way you render from scene to display referred is subjective and open to interpretation. This is why we have different LUTs and transforms (ACES / ARRI Photometric / 'Davinci' etc etc). I would like to choose LUTs that give the results I want and am familiar with which means I have to look to disable the output DRT completely.
In an ideal world, I would be able to add to the output DRT list by incorporating LUTs / transforms of my own into the software in the way that Baselight does. Then I could use the colour management end to end.
In the meantime I'll go with these workarounds.

You bring up fair points.
I also don't fully understand what DaVinci DRT means on the Input side of things but I think it's designed specifically for the timeline working luminance of which I also yet have to understand it's full purpose.
It might be that it exists for inverse transformations? I know you can do this with ACES but maybe Blackmagic seperated those two for particular reasons. Maybe workflow flexibility/freedom.

What I'd like to see is implementation of OCIO. This would play a lot nicer if you'd also leverage Fusion in Resolve as it's the only available management if you want to use ACES and also enables you to use any other color workflows.

If you feel the same maybe giving a +1 here helps
viewtopic.php?f=33&t=133121