Thanks for the link to the linearization thread -- I had not read that before.
I see now that you've gone through all the math of color spaces etc.
My main comment on the linearization issue is I don't think that the straight-line is the best approximation
for the best perceptual match. But neither is the S-curve concept. The white end of the range
behaves (perceptually) very well, so a straight-line is fine for that end -- in fact simple luminance
scaling is built into the whole ICC profile concept. Only the dark end is problematic and not
addressed in the ICC -- which brought up Adobe's BPC algorithms. So the perceptual curve needs
to compress the shadows, make the mid tones stay in the same place, and the highlight go
straight to the dmin value. You can look at my generic ICCs Gray Matte Paper and Gray Photo Paper
in the ColorSync Utility. See the xTRC tag for the graphs -- this are not exactly the same as your
graphs since one of the axes is K values not both L values. So an L=50 gets converted into the K
value that produces L=50 in the driver (i.e. print). Anyway you can see the shape of the curves.
I guess one could debate whether this is the "ideal" transformation but it is the BPC algorithm and
does seem to produce a reasonably good match visually.
There's a lot of hard to decipher stuff in this but the bottom line is scale in Luminance Y -- the
very last section 7.3 step 3.
The other issue is the AdobeRGB vs sRGB for Mac drivers. With Apple's Cocoa API
the idea was to always manage the color with ColorSync. So the default was to always convert
image output to a standard profile and let the driver handle anything special. This works great for
displays and virtually all the screen stuff in OSX is nicely color managed.
Up through Leopard 10.5 Generic RGB (a gamma 1.8 profile) was the "standard" profile for Mac print drivers.
After that (Snow Leopard) Apple decided that sRGB (close to a gamma 2.2) would be the standard.
As a driver writer you can actually select which one you want but default of sRGB is the norm.
The Epson driver lets you choose this if Printer Manages Color is on, and Color Matching is set
to Epson Color Controls. This all makes third party papers and custom ICCs problematic -- its
just not geared to the idea very well. But over the last few versions of OSX, CS, Epson, they
have managed to make a special program ACPU, a Photoshop Manages Color option, hidden flags
in the Print settings, and Epson driver NoCM option (forced) to allow custom ICCs for color.
B&W is a bit strained in this though -- ACPU doesn't work, the hidden flag doesn't work, and
the NoCM is forced/ABW disabled. Apple also created a new profile called Generic Gamma 2.2 (horrible
name since its not a gamma function) that mimics the shape of the sRGB profile but in grayscale.
Looks like Epson has matched the sRGB for ABW river -- but it would be interesting to see what
they do with matte papers -- straight-line, compressed shadows.