Blender Octane : Aces Pipeline Issue

[Concrete-Imagination]

Hi,

I'm trying to check my ACES pipeline for a project and I didn't manage to reproduce what I got with Cycles.

My workflow is : Conforming in Resolve ACES CCT and vfx plates exported as ACEScg (EXR half-float) - CGI in Blender, exported as ACEScg (EXR half-float) - Comp in NUKE also in ACES - Grading/Mastering back in Resolve. My view transform and mastering is in Rec709

For testing it I always made a simple "blank test" : I export a single frame according to the pipeline (ACEScg), import it in blender, render it back and check in resolve if I got a perfect match.

With Cycles I got no issue : I use the "image as plane" with shadeless option to import it and I tag ACEScg as IDT for the texture.
I install an ACES OCIO for overriding the native blender color management, export it and I got a perfect match.
I also always check with a colorchecker exr file also in ACEScg


But I didn't manage to make it work with Octane :

In the addon preference I use the "other config file" option with the same OCIO I use with Cycles.
For the other option I try with both "automatic" and manual with "ACES2065-1" as an entry for Manual(Octane) ; and both "ACES2065-1" or "[COlorSpace]ACES-ACEScg(ACES)"
I also deal with the Octane Imgager : using ACES:Rec709 as OCIA view (but it is only for viewer isn't it?)

For the plate, as the image as plane didn't work in Octane, I just create a plate at the good ratio and apply the texture as a RGB image.
I use a "OCIO color space" node tag as ACEScg in the Color space input socket of this "rgb image" node

For cheating the shadeless option : I use a diffuse material with roughness at 1 an use the emission input socket.
In the texture emission node I put the power to 1.

At last, for the rendering, I check the octne output option in the output properties tab
with:
file type : "EXR"
bit depth : 16-bit(floating point)
Color space : "ACEScg"

But, when I render the image, I got no match with the original plate.

Can anyone help me with that : I try a lot of variation but there is too many tweaking possibilities (issue with colormanagement, with the shader, with the render settings)...
I really to use blender octane for the project I am supervising but I need to be first 100% sure for the ACES pipeline

Thank you by advance

[Concrete-Imagination]

Thanks for your answers :

To answer your returns :

1-) First, No probem to show you the differences but I don't know how to incorpore images in this forum. Do you know how to ?
I know normally there is nothing to "tweak" that's the problem !!
The fact is no that as you wrote "it shouldn't make a huge noticeable difference" but in fact I should have 0% difference: It is mandatory for a movie pipeline. And I can get that easily with cycles. Of course I check with my scopes (waveform/parade/vectorscope) not my eyes even I work with a 10bit 4:4:4 clean feed from a decklink.

2-)About the "cheating" : well I was searching a way to show the image not influence by the 3d environment. A classic way of doing that in Cycles is to use a emission node, turn the strength to 1 and kill all lighting environnement from the scene. So I try to reproduce it in octane, but I am not sure the 1 value is correct from an octane point of view.

3-) Yes the environnement is on Raw
Thanks a lot for the links but I already read them and they give me no clue (nether the -at least- 20 other text/tutorials found on the subject).

Do you have more insight on how to achieve that ?
Thank you once more for your answers