Grayspaces, ICC Profiling, Color Management

I think the best way to view all this is that there are multiple layers, each of
which have specific roles and definitions.  Then there are conversions from
one level to the next -- color management and print or screen drivers.

(1) File level
 At the file level the pixel numbers have "profiles" that tell what the pixels mean.
This is the function the gray spaces and the color spaces.  Whether you are in
GG 2.2 or Dot Gain 20 or Gray Lab determines what the grayscale numbers mean. 
Similarly AdobeRGB or sRGB or ProPhotoRGB tell what the RGB numbers mean.
These are all "idealized" profile spaces, they are not tied to a particular devices.


(2) Actual input values to a driver -- print or screen, gray or RGB
In general these tend to be hidden, you don't necessarily know these values.
These are tied to a device but are basically a high-level description of what
you want.

(3) The lowest level is the nitty-gritty of what the device needs -- number of
drops of each ink, or screen control lines etc. 

Device drivers are the most visible piece of code.  They convert from (2) to (3).
The regular Epson driver expects RGB input and converts to K,C,M,Y,LC,LM,LK
output in a way that is optimized for color printing. QTR expects a gray input
and converts to K,C,M,Y,LC,LM,LK output in a way that is optimized for B&W
printing.  The new Epson ABW mode is like QTR -- gray input and optimized
for B&W printing.  The Black Only printing available in some drivers is also similar.

The Epson drivers are all "black boxes" -- you can't see or control the actual
conversions.  QTR on the other hand is very open, so if you want you can see and
manipulate all the internal conversions, making is possible to do-your-own.
QTR curves or QTR profiles are the guts of the conversions.

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ICC Color Management is the connection between (1) and (2). It's a wonderful
concept but since it's been introduced over time there are various places that
it can be done.  Just in PS you can Convert explicitly or use the Print Space when
printing.  The OS's support it some places and drivers sometimes support it, too.
This is the source of the "double profiling" problems -- you really don't want to
convert from (1) to (2) multiple times.  For PS I think by far the most popular is
in the Print Space but if you are not printing with PS you may have to convert
explicitly.

For the color world Color Management is pretty much a given everywhere.  
Every device has profiles built for it.  These profiles describe the correspondence
between the level (2) values and universal color values -- Lab or XYZ. 
The ICC definitions are include B&W, RGB and CMYK but in general all the well-
known profiling packages concentrate on color rather than B&W.  B&W is
somewhat simplified compared to color but it has it's own unique characteristics.

QTR-Create-ICC is a new tool to expand full color management to a true B&W
workflow.  The current version creates profiles for the printing side.  A soft-
proofing version is coming soon.  The concept is identical to making color
profiles -- print a target without CM, measure it, create the .icc file.  Then you
just print using that ICC profile.   For now I'm just bundling the QTR-Create-ICC
with QTR Printing but it is truly a completely separate function.  It is usable with
any B&W workflow -- i.e. any driver that takes a grayscale input can benefit.
QTR is one such workflow, but Epson ABW or BO are perfect candidates. 
Lack of grayscale ICC's are the weakest point of the ABW currently (IMO).

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A potential source of confusion is that the Linearizing and ICC Profiling procedures
are very similar.  In both you print the same target and read it the same way.
I think the way to think of it is that the Linearizing is part of the QTR driver. 
It linearizes from dMin to dMax of the specific paper and ink so the driver can 
give consistent results.  This is the (2) to (3) conversion from above.

The ICC profiling is for the upper level (1) to (2) conversion by the CM.  Here
you are characterizing the driver in a profile that the CM can use for conversions.
There are also a couple of other things that are useful.  You can ICC profile with
any settings of the QTR driver -- for instance QTR profiles are linearized
individually but you can ICC profile any Tone Blend or Ink Limit Adj.  If you have
a favorite setup you can specifically ICC profile that -- when the soft-proofing
is done this will be more obviously useful.  And of course the fact that the
profiling can be used with other drivers is a big difference.

Roy