ACES working space?

I'm a bit confused how "working space" is determined in Fusion in Resolve. In Nuke or Maya/Arnold you set your working space separately, then all imported files get assigned an input space and you set the viewer to match your monitor.

If I want to work in ACEScg in Fusion, do I have to use an OCIO Colorspace node on every loader and set them to output ACEScg? Would that mean I'm now "working" in ACEScg? Then to see the correct colors on my monitor I'd use an OCIO viewer LUT set to ACEScg input/sRGB output? Thanks!

That's how I work. But I neither understand nor trust Resolve's color management system, so I turn it off. I have no idea how it interacts with the Fusion page.

That's how I work. But I neither understand nor trust Resolve's color management system, so I turn it off. I have no idea how it interacts with the Fusion page.

Thanks for the confirmation!

If you're using a Loader and your footage is not ACEScg then yes, you need to convert it using an OCIO node. The Gamut node also exists and is faster but doesn't provide the same options as most ACES config files.
The Color Space Transform and ACES Transform are also available in Resolve which, again, could be faster than the OCIO tool but there is some Resolve tone mapping going on in the Color Space Transform tool that you need to be aware of.

If you're in an ACES Color-managed project and bring in your footage through MediaIns then it should convert them to ACEScg automatically. BUT they will assign the wrong viewer LUT. This won't mess with your actual footage but you need to manually change to the correct ACES ODT if you want to see the right colors. For every single Fusion Clip in your timeline (and last time I checked it will also reset on reopening Resolve so you have to do it again.)
To this day I truly don't understand why a (mostly) Color Grading application set's the wrong viewer LUT...
Maybe because the Color Space Transform Tool doesn't work as a viewer LUT? I don't know... but the end result is that working in Resolve Fusion is too cumbersome for such projects for me so I do it in Fusion Studio instead. (There are more reasons for me to work in Fusion Studio but the few times I hoped to benefit from the Fusion clips in a Timeline ended up being very frustrating due to the color mismatch)

Thanks! Haha, all sounds like typical color management total chaos... I'm testing out Fusion for now, using it on smaller projects to see how it feels. I'll definitely upgrade to Studio when the time comes, being standalone seems like a big improvement.

I'm a bit confused how "working space" is determined in Fusion in Resolve. In Nuke or Maya/Arnold you set your working space separately, then all imported files get assigned an input space and you set the viewer to match your monitor.

If I want to work in ACEScg in Fusion, do I have to use an OCIO Colorspace node on every loader and set them to output ACEScg? Would that mean I'm now "working" in ACEScg? Then to see the correct colors on my monitor I'd use an OCIO viewer LUT set to ACEScg input/sRGB output? Thanks!

That's pretty much how it works yes.

I think Noah is spot on with the explanation.

To this day I truly don't understand why a (mostly) Color Grading application set's the wrong viewer LUT...
Maybe because the Color Space Transform Tool doesn't work as a viewer LUT? I don't know... but the end result is that working in Resolve Fusion is too cumbersome for such projects for me so I do it in Fusion Studio instead. (There are more reasons for me to work in Fusion Studio but the few times I hoped to benefit from the Fusion clips in a Timeline ended up being very frustrating due to the color mismatch)

I may add..
It doesn't really matter if you work in Fusion Standalone or ReFusion. The way Fusion is designed doesn't allow you to run OCIO on a project wide level like Nuke or most other OCIO supported apps. You always set up management manually. But yea the fact that they ported this straight into Resolve without any design considerations is still a big problem to this day when wanting to work with Resolve color management.

A summary of the issues I know of:
- Resolve doesn't support OCIO management
- ReFusion only partially supports RCM/ACES in the sense that the Fusion working space is automatically the linear variant of Resolves timeline working color space. Somewhat makes sense but you don't have control over this within a system that expects you to manage manually.
- ReFusion viewer LUT doesn't support the ACES Transform & CST so it's impossible to use ACES/RCM with Fusion unless you create some custom LUTs or use OCIO configs to work in the viewer.
- OCIO ColorSpace on the viewer does work but OCIO configs are external to the software. You would expect ReFusion to be able to work natively regarding dependencies for both RCM and ACES.
- Unlike the Fusion node tree, OCIO File Transform on the viewer only processes data from 0-1 so custom setups with 1d LUTs for example are out of the question.

And yea the most simple steps forward would be to just implement both the ACES Transform and the CST into the viewer. This would tackle most of the issues. But ultimately a proper color management system that works fully in line with Resolve is what's needed if they insist it should be integrated into the Resolve ecosystem.

Thanks for the interesting comments, Shebanjah. I guess this all leaves me with one question: what IS the working space in Fusion in Resolve? I checked the manual but no results for "working space." If I convert my incoming images to ACEScg and they're processed in yet another space, might as well convert them to that to begin with.

"Working space" is the space where you do the work, nothing more. In semi-automated CM systems like Nuke ACES implementation, working space is a default that readers convert data to and writers convert data from. But you can manipulate all conversions manually too, thus using whatever the space is you convert to. That becomes your working space. In Fusion, if you manage the transforms yourself, it is up to you to make sure all data is converted to same space. What that space is is fully up to you again. In Resolve Fu, timeline colorspace used to dictate the gamut and transfer function was linearized, but in 18.1 that changed now to god knows what.

Data itself does not have colorspace, it is just numbers. How you interpret those numbers is what attaches color related meaning to data. For the same reason generators generate data in any colorspace, because it is up to user to give meaning to raw values through interpretation. If you interpret them to be lets say ACEScg, so be it. But they can also be sRGB, and you can move them to ACEScg by applying sRGB > ACEScg transform. And generator itself changed nothing, what changed was the interpretation of the data, how you decided to handle it.

For example render engines work the same way, they don't have any specific working space, they just crunch numbers. If all textures and generators (like procedural shaders etc) are in colorspace X, resulting image will also represent light calculation in colorspace X. But if textures are in Y, so will be the result.

Got it, thanks, makes perfect sense!