ACES background document

[Christopher]

I meant this post; ACES background document - #6 by Alexander_Forsythe both images are the same, how did you achieve this ?

[shebbe (Shebanjah Klaasen)]

They aren’t fully the same but I think there isn’t much more to it than what Christophe explains.

@ChrisBrejon

• One is rendered with ACEScg primaries displayed in Rec.709 (ACES).
• One is rendered with BT. 709 primaries displayed with a BT. 1886 EOTF.

So the ACES version uses the same rgb values input as surface colors as the other but because rendering in ACES means that colorvalues are considered ACEScg (AP1) instead of Rec.709 (unless the sofware is setup to manage otherwise). They weren’t converted from Rec.709 to AP1 before rendering.

Christophe also has a blog covering CG with ACES which I found to be a great resource.

[ChrisBrejon (Christophe Brejon)]

So, these are like two complete different setups.

• One has ACEScg as a working space and so I use ACEScg primaries in the cornell box and display them with the ACES (Rec.709) Output Transform.
• The other has “sRGB/BT.709 - linear” as a working space. So I use sRGB/BT.709 primaries for the Cornell Box and displays them with a BT.1886 EOTF.

The idea was indeed to show how close they were visually and see if it would generate any kind of discussion or investigation. Could be interesting to check these renders with the three candidates possibly ?

Chris