QTR-Quadtone RIP

Andrew Maier <andrew@...> wrote:

> **
>
>
> ...
> > See http://www.paulroark.com/BW-Info/UT-3D_Readme.pdf for a description
> of
> > the inkset. Profiles are available for downloading. Although I don't have
> > one for Ilford Galerie Gold Silk, take a look at the curves for similar
> > papers. Starting with one of those curves would make sense.
> >
>
> ...
> > > I now would like to profile the the Ilford Galerie Gold Silk (a baryta
> > > paper, which I rather like), but when doing so I get LAB values which
> are
> > > inverted at the black end (See results as the bottom)....
> > >
> > I suspect you are not turning off the Eboni. The driver injects Eboni MK
> > as the 3 color curves approach the black point. You stop that by having
> > one of the inks head back down, ultimately to 0 at the 100% black input
> > point. See the curves I've made for the inkset and glossy papers. (Let me
> > know if there is a problem with the pre-zip file method I used for
> > downloading.)
> >
> > If you are turning the Eboni off, then the other options are that the ink
> > load may be too high for that paper. Which paper type is specified in the
> > driver alters the ink limit, and you can also lower the black ink load by
> > having the Green curve (Magenta ink control) stop at 90%. That is, when
> > the input is 100%, have the Green curve only at 90%. Be sure the blue
> > (and/or red) curve(s) are totaly "off" by that point. You don't want the
> > driver to put any Eboni MK into the mix.
> >
> >
>



> How do I do this? I am using a Mac (10.7) with Photoshop CS5.
>


I don't know Mac, but the use of curves in CS5 is probably the same on both
platforms.



> When printing the grey scale wedge, I set the Photoshop print dialog to
> printer manages colour and then disable colour management in the printer
> driver printing dialog. When I do this I do not have any access to the
> sliders to control the amount of ink. So I cannot turn off the Eboni Ink. I
> assume I am missing something fundamental here.
>


The Epson drive cannot turn off the Eboni.  The PS curves can.

Ultimately, you want to embed PS curves in an ICC using QTR's Create
ICC-RGB.  So, you want PS to manage color, not the printer.  How that is
done on a Mac, I'm not sure.  On Windows I do this in PS.  The "Print" box
has option:  PS controls color v. Printer controls color.  In the latest PS
and OSs, I can't combine ICCs with "Printer controls color."

So, be sure you are in a mode where you can pull up an ICC.

Once in that mode, in PS, with the image in Adobe RGB (1998) work space,
apply a straight-line curve that has the Green curve going from 0 to 100.
 The other curves are pulled flat.  Print a 21-step with the resulting
Green 21-step image.  Additionally, you ought to try a 21-step with the
Green and Red curves both going from 0 to 100.  Here, the Blue curve is
"off" -- flat at 0.   This 21-step image will look blue on the monitor.

With both of the prints that result from the steps above, measure the lab L
or density of the steps.  Where is the dmax reached?

In both of these cases, by having on channel of the RGB image off at
wherever the dmax is reached, you've turned off the Eboni.  The dmax will
be generated by the glossy inks.  Where they reach their dmax will become
the setting for the end of the curve that controls the colors and other
aspects of the final ICC.

You can see from the glossy curves in the 3D profiles zip how I've pulled
the Blue curve down to 0 to turn off the Eboni.  The trick is to do it in
the deep shadows so the reduced Lab A is not seen.  It will actually result
in a deeper looking black.



> Some more observations, I just realized that the black 100% square still
> smudges even after having dried for more than 24 hours.
>

If there is much Eboni in the mix, it'll never dry right.  Eboni rubs off
glossy paper.


I have now replaced the MK ink cartridge with the PK cartridge and have
> printed a new strip.
>

That should be fine, but, of course, it eliminates the ability to print a
good matte paper print.

Paul
www.PaulRoark.com


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