[argyllcms] Re: Gutenprint and ink limits.

Am 08.08.07, 11:25 +0200 schrieb Lars Tore Gustavsen:

> The resulting tif file looks very similar to the Step-21-gray.tif
> provided with qtr, but as a bonus I now had a ti2 file.  I opened this
> file in photoprint, since cinepaint have problems printing grayscale
> images, printed it (with option "uncorrected") and measured it.

You'd have to convert to Rgb by hand in CinePaint.

> gutenprint            100.00  1.827   12.54   -3.70   1.19
> gutenprint density+10 100.00  1.893   11.12   -2.68   -0.53

Can you verify that you have not just a K only print and CMY is involved.
You would perhaps need a strong magnifying glass to see something.

> windows abw           100.00  2.421   3.42    -0.11   -0.22
> windows "no color"    100.00  2.122   6.83    -0.36   -0.27

> Am I right in guessing that I should lower this value before I try to
> profile my printer?  I guess it most be at least possible to match the
> normal windows driver with lab 6.83.

Sounds reasonable. Not shure how lustre looks like. The relation of the 
Gutenprint to the windows L value is what I see from a pure K compared 
with a 100 60 0 100 rich black colour patch on glossy with K3 inks
  L*16.9 -> L*5.8 (including strong colour casts).

> Maybe this topic about deep blacks is a b&w issue? Or is a general
> printing issue?

You definately need a rich black. K only is not enough for dark patches.
Whether PhotoPrint uses CMY for Gray scale images must be checked. 
Alastair ?
In CinePaint you can set each Cmyk channel for its own to verify.

A patch set of mainly poor and intermixed Cmyk ramps should suffice for 
determing ink limits. Unfortunedly I did not find a option to targen for
generating the intermixed rampes. Possibly I have something overseen?

kind regards
Kai-Uwe Behrmann
--
developing for colour management 
www.behrmann.name + www.oyranos.org + www.cinepaint.org

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