I’m trying to understand better exactly how profiles are constructed and how they work. I’ve read Anatomy of a Profile and a few dozen other articles on the Color Wiki.
I have watched your Rendered Gamut video (which I enjoyed) and understood what you were showing. I also read Myth #26 and understood that, but neither answered a question I have. Steve touched on the “rendered gamuts” in that article, but didn’t go into what they actually are.
When I view a 3D graph of an RGB printer profile, it defaults to “Device Gamut”. I understand that this is the same as the Abs Colorimetric rendering.
What puzzles me is that if this is the device gamut, or the maximum this printer/paper/ink combination can do, then why do Perceptual, RelCol and Saturation 3D views of the profile display larger than the AbsCol rendering? Exactly what am I viewing when plotting those rendering intents?
RelCol looks like AbsCol, but the white point is raised to 100L* instead of the paper white (which is about 96L* in this profile. It also looks like RelCol provides extended Chroma compared to AbsCol, mainly on the lighter end of the tonal scale.
When I plot Perceptual, it looks like the L* range goes from 0 100 and I get even more Chroma than RelCol. The perceptual view completely encloses the AbsCol view by an almost equal percent all the way around.
These plotted “gamuts” are larger than what I get when I convert a wide gamut, ProPhoto RGB color list to the same profile using Perceptual or RelCol. Those points, when plotted, fit nicely into the Device Gamut (AbsCol) and take most of the points out to the gamut border (like in your rendering video).
I think if I understood exactly what these Perceptual, RelCol and Saturation 3D plots represent, it would help me fill in some gaps in my understanding.
Thanks for your help.