QTR-Quadtone RIP

Thank you Roy. That's the key. Sitting around and waiting for my train
I thought about the problem and found out, that the non-linearity
looks like some sort of gamma applied to the cuve.
Thanks for your excellent explanation. Now I am back on the right way.
Your introduction helped me a lot to understand how it works.

My next step will be to profile my papers for QTR itself. But this
won't happen until my next vacation. My first testprints with the
preprofiled EEM look greath and even more neutral then Epson ABW.

$50 for your greath RIP and help are on the way.

Gottlieb


--- In QuadtoneRIP@yahoogroups.com, "Roy Harrington" <roy@...> wrote:
>
> Hi Gottlieb,
> This is a good set of questions and I think leads to a good
introduction on
> color management.
> The idea of color management -- i.e. using display and printer ICC
profiles
> -- is to match
> L values from the original file.  This is different than making L values
> linear.  The
> stepwedges have K values that are linear but depending on the
profile the L
> values
> may or may not be linear.  When a file such as the steps you're
using has no
> embedded profile
> it inherits the gray working space defined in Color Settings.  Not
knowing
> your settings
> makes it hard to evaluate your results.
> 
> So what you see on the screen depends on the Color Settings -- vary the
> workspace and you'll see.
> Printing however depends on the selections on the Print page -- No Color
> Management means
> the Color Settings have no effect on the result.  A Print Profile
means that
> the workspace
> is involved in the output.  The idea being that you want the display
and the
> print to match.
> 
> The idea in making the ICC profile with (1) and (2) is to have a "known"
> value sent to the driver,
> hence the linear K values are sent to the driver.  But in using the
profile
> in (7) and (8) the CMS
> is trying to match the L values of the input in the print by
changing the K
> values sent to the
> driver.  (Note in (7) "without CMS" isn't really true because the
working
> space will be used).
> 
> So it's hard to say whether the new densities you got are "better".  The
> most important criteria
> is which stepwedge print matches (i.e. looks) the closest to what
you see on
> the screen.  I suspect that
> the random stepwedge is not a very good image to evaluate this. 
Possibly
> the "21step" file with
> the steps in order is better or maybe a real image.
> 
> It's a bit hard to accurately measure this because the idea is a
> "perceptual" intent not a straight-line.
> But since you using a photo paper with a very dark dMax you can get
pretty
> close to the straight-line
> test by using the QTR-Gray Lab profile for the gray working space in
Color
> Settings.  This still
> isn't perfect since the mapping of L=0 of the file to L=3.xx of the
print
> adds some non-linearity.
> 
> Roy
> 
> On Jan 6, 2008 2:57 PM, g.bossert <g.bossert@...> wrote:
> 
> > Hello,
> >
> > my name is Gottlieb and I'm new in this group.
> >
> > I'm trying to create some grayscale ICC profiles for the Epson 3800
> > ABW driver using the QTR-Create-ICC.exe and Datacolor Spyder3Print
> > (also knwon as PrintFix PRO with the Datacolor 1005 device).
> >
> > On my glossy proof paper the Epson 3800 ABW (dark setting) is almost
> > linear as it should be.
> >
> > The generated Grayscale ICC Profile should only correct the L* curve
> > only marginally. But instead it seems that the calibration does the
> > contrary.
> >
> > But may be the caibration does all right and I make an error in
> > reasoning or calibrating.
> >
> > The way I created the grayscale ICC profiles was the following:
> >
> > 1) Open the file "Step-21-gray.tif" in Photoshop CS2 without CMS
> >
> > 2) Print it with no CMS and the Epson 3800 ABW driver set to the
> > setting "Dark"
> >
> > 3) Let the print dry over night
> >
> > 4) Read the 21 Patches with Spyder3Print and save it to an Create-ICC
> > formated file.
> >
> > 5) Drag the file to QTR-Create-ICC.exe
> >
> > 6) Install the Profile
> >
> > 7) Open "Step-21-gray.tif" in Photoshop CS2 without CMS
> >
> > 8) Print it with CMS managed by Photoshop, the QTR-ICC pofile and the
> > Epson 3800 ABW driver set to the setting "Dark" with the same media
> > settings
> >
> > 9) Read the 21 Patches with Spyder3Print and save the L* vaules to an
> > file.
> >
> > 10) Import the L* Values from the file of step 4 and 9 into an
> > spreadsheet an compare them
> >
> > The resulting graph and the L* values can be found here:
> >
> > http://www.ironsys.de/pub/yahoo_qtr_group/profile-graph-1.gif
> >
> > (The color profile was generated with Spyder3Print)
> >
> > I hope someone can help me.
> >
> > Thanks,
> >  Gottlieb
> >
> >
> >
> 
> 
> [Non-text portions of this message have been removed]
>