I’m slowly figuring out ACES for my personal VFX projects, but the past couple of days I ran into some trouble with how white values work with ACES. I’m using Fusion (but the same applies in Nuke, I checked), and when I add a simple white Background node (constant), what Fusion considers 100% white is actually grey, when outputting Rec.709 from ACEScg.
I read around here and messed around in both Fusion and Nuke to understand this better, and I understand that ACES allows for much more data to exist beyond the value of 1.0, but this is still leaving me confused. How should I go about compositing when working in ACES?
I’ve created a little test comp with some footage from my Blackmagic Cinema Camera 2.5K (RAW footage) and some Light Rays. Looking at the linear image, the light rays are beautifully blown out, like I want them to be at the source, as it’s simulating the look of pointing the camera at a bright light, which is what I’m after, but when viewing the composition after the ACEScg>Rec.709 ODT node… it’s all wrong.
Every node in the flow that uses white values are inherently much darker, so everything looks dull and almost transparent, far from the blown out highlights look I’m going for.
My test comp is of a hologram screen, basically. The hologram is made of white lines and a strong blue light emitting from below it, the source of said light I want to look blown out.
So I understand there’s a reason for how ACES works, but what’s the correct way to composite with this in mind? If all my white constant nodes are not white anymore, if matte nodes aren’t white anymore, what’s the right way to work?
I tried doing something suggested in another post here, converting some nodes from sRGB to ACEScg to “correct” the values, but this only works in a few cases. In other cases, it destroys the data basically. Some nodes only have simple colour values, like constants, but some are more complex, and using that “correction” on them can really destroy their effect.