No. The IDT always comes first. It is the Input Device Transform, and is what takes the image from it’s native colour space into ACES.
Some implementations may hide some of the steps from the user, but the full sequence of operations is as I describe it.
I am describing it in full because that’s what you need if you want to build it yourself. IDTs transform to linear ACES, so you then need to go from that to the ACEScct working space before applying your grade. The input to the RRT has to be linear ACES, so you need to go back to that after the grade.
If you are building a Rec.709 LUT for LogC from the CTL files, for example, they need to be these operations in this order:
- Look_Grade (as CDL, CLF or whatever)
And that’s without any LMT, such as a “show LUT”, which if implemented as per spec should go between steps 4 and 5.