In 2021, around version 3.point.something, Redshift changed its default color space from what it called “scene-linear Rec.709-sRGB” to ACEScg. The mouthful “scene-linear Rec.709-sRGB” just means a linear color space defined by the sRGB primaries (which are identical to the Rec.709 primaries). ACEScg is also a linear color space (i.e. gamma = 1.0) but with different primaries (specifically, the AP1 primaries), yielding a broader color gamut than the sRGB / Rec.709 primaries.
If you’re using DaVinci Resolve to muss with your newly ACES-compliant Redshift EXRs, then you need to change your color settings to something like those above. Otherwise ain’t no way your Resolve timeline gonna look the same as your Redshift render view.
Gotta be ACES for color science (ACEScc or ACEScct – both non-linear and subtly different). Don’t think it matters which version number of ACES you pick. Do need to set ACEScg for the input transform, so that Resolve knows to expect ACEScg in, which is what Redshift is now giving it by default. The ‘cg’ stands for computer graphics BTW.
The output transform should be set depending on how you want to output the file, as normal. sRGB for computer use, Rec.709 for SDR TV, etc and some flavor of ACES if the output needs to stay in an ACES-compliant pipeline.
Still hungry? The Wikipedia entry on the Academy Color Encoding System (ACES) is here and the Academy’s own marketing website is here. More on gammas, gamuts and other over-complicated color stuff here.
