Digital BW, The Print

Hi Gurli

> (Are the profiles on the Epson
> 2200 driver and download page by Bill Atkinson?)

Bill's Epson profiles are available on the Epson USA site somewhere.  They
are not pointed to from the UK website so I don't know exactly where.

> I am a fairly advanced Photoshop user and I think I am able to
> convert beautiful b&w images in PS. I also do a lot of color
> printing on my 2200 with Epson and other paper company's
> profiles, 
> and I think they come out beautiful.

The good news with QTR is that it is now, essentially, a colour-managed
workflow.  So think about it in the same way as you would print colour with
an Epson ICC profile - using PS to do the profile conversion and "no colour
adjustment" in the Epson driver.  So if you are up on colour management then
you are an inch away from great results with QTR.

Think of the two ICC profiles... QTR-Gray Matte Paper and QTR-Gray Photo
Paper..... as being a generic matte paper profile (like Epson's ICC profile
for Epson Enhanced Matte paper) and a generic photo paper (like Epson's
profile for Epson Premium Semi-gloss).  Roy could have done a different
profile for every different paper but since B&W is simpler than colour (we
are only worried about tonal compression in one dimension: luminance or
print reflectance) it wasn't really necessary.  That sort of refinement can
come later.

So the workflow is exactly the same as for colour.  Exactly the same as for
Epson but with a different driver - one that manages the inks in a better
way (and one that is flexible in handling different ink sets).

> When you convert, do you use dither?

I use a Mac and so I can convert the profile on the fly with PS as PS hands
the file off to the QTR driver.  There is no dither selection at this point.
If you are on a PC then you need to do the conversion using Image -> Mode ->
Convert to Profile and then save this "print" version before opening it in
QTR GUI.  To be honest I do not know what Use Dither does - it defaults as
checked in my system and so unless someone here says not to use it I would
use it.

>I thought the profiles
> for PS were for soft proofing only

They are ICC profiles which depict the nature of the print space - just like
colour.  You use them at printing and as a soft proof of what the image will
look like once converted to the print space.

So to summarise your experience.  Firstly, you printed with the Epson driver
and Epson matte paper profile and used colour management tools (perceptual
intent) to handle the compression from the broad workspace to the narrow
tonal range of the print space.  Result: good management of tonal
compression (yay perceptual intent!) but bad Epson use of colour inks.  Then
you printed with a RIP that makes good use of the inks but you forgot to
make use of the tonal compression tool available to you.  Result:  good
"colour" (no castes) but bad tonal transform.  Thirdly, you printed using
that good driver which makes good use of the inks AND you made use of PS's
access to perceptual intent to handle the tonal compression.  Result:  great
prints.  Go on and explore!

Cheers

Steve

PS Please trim your posts



Completely Optional Learning Exercise:

If you want, you can take some of the voodoo out of what you're doing and
why the ICC profile made such an immediate difference with a simple exercise
if you know how to use Excel or an equivalent spreadsheet program.  It is
also a prerequisite for anyone thinking about writing their own curves - if
they want to understand the process rather than just follow instructions.

While you are happily printing, I would encourage you to think about what I
said about the nature of the print space and its construction.  Rips like
QTR (or IJC/OPM) are "calibrated" such that they print a greyscale from ink
black to paper white with nice even increments of L*.  (L* being a measure
of luminance in Lab terms). So on a chart, for matte paper L* is a straight
line from around (0,16) to (100,96)...whereas true Lab would plot L* from
(0,0) to (100,100).  The process of making sure L* is linear from black to
white is called linearization.  You will come across this term on this forum
a lot as people who are making their own ink curves "linearize" their
curves.

Even though the printer produces linear L* from its best black to best white
just like the Lab space you can see from the chart that the two spaces are
not the same - the best blacks and whites are different.  In fact, knowing
that the higher L* is the lighter the shade of grey is, you can see why your
first prints were generally "lighter" than you expect looking at the screen.

If you are so inclined, and this is a very informative exercise, do a very
simple Excel spreadsheet.  Put in the first column steps from 1, white, to
21, black, in 5 point increments - just like a 21-step wedge. Make the next
column "True L*" - it goes from 100, white, to 0, black, in five point
increments.  Make the third column "Output L*".  We could measure an actual
step wedge printed with a linearized QTR curve (without the ICC profile
conversion) but given we know that the print setup has been linearized and
that dMax for matte paper is around 1.65 or L*=16 and paper white is about a
density of 0.03 or L=97 we can simple make this column go from 97 to 16 in
even decrements over the 21 steps as a good enough assumption.

(If you are on a Mac take a look at one of the matte print curves, eg
UC-EEnhMatte-warm-1.  Look at the last line and you will see the linearize
function with a density number of around 0.03 at the beginning and around
1.65 at the end.  This is simply the density measurements the person writing
the curve took from a step wedge printed before the linearize function was
inserted.)

Now convert the two columns of L* - "True" and "Output" to density.  This
involves a two step process first calculating the XYZ space equivalent of
L*, ie XYZ_Y, and then from this calculating density.  I'll put the two
formulas at the bottom of this post.  Now plot the two density curves, steps
on the x axis and density on the y axis (you have to fudge the True L*=0
Figure because it is infinity).  The curvature in these two curves is gamma.
You can now see why the prints were "flatter" as well as lighter - the
curvature or gamma was not as great.

Ok last step.  Take a look at the XYZ_Y values you calculated for Output.
Plot this.  Now, find the QTR Gray Matte Paper ICC profile on your computer
(on a Mac they are stored in Library->Application Support ->Adobe ->Color
->Profiles).  On a Mac you can open this with Colorsync Utility by
right-clicking or command-clicking).  Have a look at kTRC.  It has a curve
which is the same as the one you just did (with one minor exception which
need not be bothered with).  You can see that the ICC profile has profiled
the print space with a T(onal) R(esponse) C(urve) or TRC and 'cos its just a
greyscale: kTRC.  

If we have a profile of the print space and we have a profile of the
workspace (Gray Gamma 2.2 or whatever) we are away laughing and can use PS's
powerful colour management to manage the tonal compression.

No more black box.



XYZ_Y = IF(L>8, ((L+16)/116)^3,(L*27)/24389)

Density = -LOG10(Y)