Re: nuke-default's sRGB and ACES 1.1 sRGB


Eberhard Hasche
 

Hi Gonzalo,

the main problem with sRGB (and Rec709) in ACES is that nuke-default is adding the sRGB-Transfer Function to the linear material,
whereas ACES is also applying a Render Transform (RRT+ODT) which deals with the HDR content, and in order to make space for the content above 1.0
a value of 1.0 is compressed to 0.8 which makes the export appear darker.

A more profound discussion is here:

https://acescentral.com/t/nuke-srgb-aces-srgb-not-the-same/2292

Cheers Eberhard

----- Urspr├╝ngliche Mail -----
Von: "Gonzalo Garramu├▒o" <ggarra13@gmail.com>
An: ocio-dev@lists.aswf.io
Gesendet: Mittwoch, 4. Dezember 2019 17:58:10
Betreff: [ocio-dev] nuke-default's sRGB and ACES 1.1 sRGB

I recently noticed a discrepancy in the sRGB output transform of
nuke-default's and ACES' one. Basically, Nuke's seems to have an
additional 2.2 gamma transform while ACES does not seem so pronounced.
What's weird is that the ACES OCIO transform matches the equivalent CTL
transform, but the nuke-default's output looks more like what is
expected of the clips I am feeding (comparing them to a sample PNG taken
from a web page from where I downloaded the clip from).

I tested the images both with my viewer and with the DJV viewer with
same results.

Can somebody shed some light into the issue?

Find attached the two images of the "problem".

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