DI working space and LUTs with EXR

Discussions - Using ACES Creative
#1

Going from Davinci Resolve non-color managed with DPX into Nuke, the LUT exported from Davinci works only if OCIOfiletransform is used to add a shaper LUT converting the working space for the LUT from the one used in Resolve (for example Rec.709) to Nuke’s linear working space. This works on the DPX file which is in log space, as LUTS need to be in log. Since this is a non-color managed workflow the DPX is read into Nuke with the input color space set to the same as the view transform.

However, when working with DaVinci color management on, with the working space (i.e. timeline space) set to the default non-log color space of Rec.709, the resulting LUT will clip exposure values in Nuke, even with the shaper converting the working space. This is fixed if the working space in Resolve (timeline) is set to log, which makes sense to me. It’s also how ACES works (the ACEScc working space being log for DI).

My question is: am I correct that if one wants to work color managed in Resolve that the working space has to be log, rather than a limited color space like Rec709 for LUTS to work? Some colorists we work with are resistant to working in log rather than Rec709, so I’m wondering if there is a workaround I am missing.

#2

Derek,
It sure seems that this is not an ACES question. It seems to be a general workflow question.
it looks like you have an dpx image that you are viewing in resolve with a lut and it looks fine.
When you take the same image into NUKE and apply the same lut, using the OCIO file transform node you are seeing something different. To address that you are applying a 1-d shaper lut.

Nuke by default enables color management. This the easiest way to see the same things in nuke and in a non-managed resolve workflow is to bypass the Nuke Color management. So on Read Node set the ‘Raw Data’ flag. Then when you go to the viewer set the viewing transform to ‘None’

The resolve color managed workflow requires some effort to use effectively. By default Rec709 will carry less dynamic range than log spaces. Working in REC 709, or any gamma space, can clamp the image data.

If the lut you are using expects a log input, than the image processed through the lut must be log. In a properly color managed workflow can do this from a variety of working spaces.

It’s a lot easier to do color work in REC709, but the state of the industry is such that, as you noticed, it reduces deliverable quality without considerable effort. Colorists who expect to have many more years left in the industry should learn to work in LOG. The colorists I have assisted in the transition from a Rec709 workflow to a log workflow have thrived. None of them have gone back to a rec709/P3 workflow.

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