QTR-Quadtone RIP

Ross,

As a general rule, whenever you are printing of step wedges to "see
what the system does"
you want to do it with No Color Management.

The inkseparation.tif file is an extra special case with bit values.

For QTR linearization the idea is printing a target using a curve with
no-linearization, no-color-management.
Reading the values, running QTR-Linearize-Data, and putting the values
into the curve produces
a correction that makes the steps linear in Lab value space.

For ICC profiling its the next level up.  Print a target using a
linearized curve(s) (blends etc) with
no-color-management.  When you run these values through QTR-Create-ICC
you get a industry
standard ICC profile that allows the system's color management to
match up the luminosity (L)
of your image file to the luminosity of your printing method.  Color
Management of your screen is already
doing this so adding this to your print workflow is what gives you
screen-to-print matching.

In some sense QTR linearization and ICC profiling duplicate some of
the functionality so that's
why some generic ICC's can be and are provided.  QTR-Gray-Matte-Paper
assumes a linear Lab curve with
a lower dMax of matte paper, QTR-Gray-Photo-Paper assumes same with higher dMax.

BTW, the standard color ICC profiling works the same way -- print a
target with no-cm, read it
and make a profile.

If you have Print-Tool and can use it for all image printing its
easier to get consistency -- for
both QTR use and color printing thru Epson driver.  If you do custom
color ICC's this makes
it easier.

Roy

On Wed, Feb 13, 2013 at 12:45 AM, rossfmj <ross.jarvis@...> wrote:
> Thank you Roy
>
> This highlights another issue which is confusing me.
>
> My understanding is that the ink separation. tif needs to be printed without colour management, so is in a way an "absolute" test.  For this I use QTR print tool.  However I thought that the step wedges were "subjective" and prints for linearisation were to be done through the process most like that of my normal workflow, so I've been doing these through Elements.  As you mention "No Color Management" appears not to be an option through Elements 11 on a Mac.
>
> Should I be printing step wedges for linearisation through QTR Print Tool?
>
> As mentioned earlier, I am not yet happy with the printing of shadows/blacks, particularly at the 90%+ values, and also the linearisation "bulls eyes" show rings and unevenness.
>
> Might I be getting too involved in the detail here?
> Do these tests show some of the limitations of UT14, particularly with profiles only using 2 inks?
>
> regards
>
> Ross
>

-- 
Roy Harrington
roy@...
www.harrington.com