Recapitulating all the color spaces involved:
- ARRI V3 Log C: uses the ALEXA wide-gamut [AWG] primaries, and a log floating-point or log 10-bit or 12-bit integer encoding. An image storage space and a grading space.
- ACES: AP0 primaries; linear floating-point encoding. An image storage and interchange space.
- ACESproxy: AP1 primaries, log 10-bit or 12-bit integer encoding. A grading space. Not an image storage space because of insufficient bit depth to guarantee lack of banding.
- ACEScc: AP1 primaries, log floating-point encoding. A grading space. Not an image storage space.
- ACEScg: AP1 primaries, linear floating-point encoding. A working space for rendering and compositing. Potentially an image storage space, but not a recommended image interchange space.
Note that the log encoding for ACESproxy and the log encoding for ACEScc were designed to work together. If ASC CDL values were created using an ACES-supporting on-set tool that had applied those values to ACESproxy images, those same ASC CDL values will produce the same visual result when applied in downstream ACES-supporting tools that manipulate ACEScc images.
Flow of color image data and metadata across contexts
There are two key principles that provide consistent color across the four contexts mentioned above:
- The same core set of transforms is used at every stage
- If a transform is parameterized (in the way that an ASC CDL transform is parameterized by slope, offset, power and saturation values, or a 3D LUT transform is parameterized by the contents of a particular 3D LUT) then the same parameters are passed from one context to another throughout production and post-production
On-set production optionally produces an on-set grade. If it does produce such a grade, then the grading parameters, expressed as an ASC CDL file, are pased from on-set to near-set or Editorial, and thence to VFX, and finally (as a starting point or hint) to the final DI grade.
Similarly, any 3D LUT that might be implementing an overall show look is applied the same way, at the same place in the pipeline, in each context.
The diagram below shows the flow of image data (and, with dashed lines, of optional image metadata) between production and post-production contexts.