Alexa 35 conversion to ACES 2065-1 - Difference on a bluesceen shot between Resolve and Baselight

Discussions - Using ACES
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Hi,

I got my hand on the first Alexa35 footage from a project that we are started to work on now.
The film has a lot of bluesceen shots. We will comp in Nuke.
We converted the footage with Resolve 18 to ACES 2065-1 in an ACES project.
The grading will be done in another post house on Baselight.

For a test we received a graded DPX (Rec.709), a ungraded EXR in AWG3/linear from Baselight
and a BLG file with the grade.

The grade with the Baselight for Nuke plug-in matches the DPX reference frames when I am using the ungraded EXR footage from the Baselight export.

But I found a difference between the ungraded EXRs from Resolve and Baselight.
The red channel and a bit the green channel is different. Its not very obvious when viewing the blue screen shot as a whole, but it’s visible in the histogram and if you look closer.

Here is a little A/B comparison from Nuke.


https://my.hidrive.com/lnk/wSULFVgI

Maybe someone has an idea why the two conversions look different?
After watching the ARRI Tech Talk from @SeanCooper I wonder about the colourspace journey in Baselight a bit. Can I always easily convert between AGW3 and AWG4? I thought this was not so easy?@daniele

colorspace_journey
colorspace_journey1028×172 51.3 KB

Best regards

Daniel

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Any chance that ACES Ref Gamut Compress is on in the Resolve settings?

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I can double check tomorrow, but I am pretty sure I checked that already.

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I guess the WG4 definition in Baselight is, at the moment, not 100% in line with the ACES D60 CAT. This will be addressed in the next major version of Baselight. It ist trivial to make custom space so the two match exactly, if this is a concern. The differences should be very small.

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Thanks for your reply.

No, I think/jope this shouldn’t be a problem for the project. I was just curious and wondered why this happened.
It’s the first time we use BLG files and for now we don’t get the plugin rendering on the farm in the pipeline.

Anyway there is so much bluescreen, it would be wise to revisit the initial foreground grade at the end of the project :slight_smile: