QTR-Quadtone RIP

Hi Jeff. I am familiar with Keith's image, but I didn't actually try
it. My reasoning: I need to create curves that will produce
(reasonably) identical prints on different papers. If I can't reliably
linearize my profiles this will be an exercise in futility. I may get
good prints, but none will match. I did also try the 51-step wedge,
but I kept getting QTR errors complaining that the linearization array
sequence was invalid because it was not constantly increasing so curve
generation failed. To be honest, I got this message most of the time
using 21 values, but did manage to generate a couple of curves. It
seems like QTR doesn't like multiple steps with the same value, or
steps that are too close together, or, horrors, a value that actually
decreases. All of these things can happen in my world, and I don't
know how to fool QTR without invalidating my measurement.
I also tried to load a Photoshop CS acv I use all the time, but got a
QTR error about invalid values. Sorry, I'm not in front of that
computer at the moment but I have captured all these errors on my home
 PC. 
--- In QuadtoneRIP@yahoogroups.com, "Jeff Randall" <jrandall@...> wrote:
>
> Phil: Have you printed Keith Coopers test image
> <http://www.northlight-
> images.co.uk/article_pages/black_and_white_test.html>
> and looked at the circular gradient and printed the offsetgrad8.jpg 
> file located in this group's Files section to see if you can 
> actually see the non-linearities you are measuring?
> 
> Another thing to try is a 51 step calibration approach using the 51-
> step file in the OneEye folder of the QTRip folder.  I had problems 
> getting a linear profile using the 21-step approach, but the 51-step 
> approach worked very well for me.  YMMV.
> 
> BTW, I stretched the 51step image to print landscape -- bigger 
> patches for my clumsy hands.
> 
> 
> --- In QuadtoneRIP@yahoogroups.com, "Philip Schwartz" <pschwart@> 
> wrote:
> >
> > Thanks Terence. I am a new to QTR but have lots of experience 
> printing
> > fine art B&W. QTR has lots of controls, but they are not well
> > documented so results are often not predictable, making the 
> profiling
> > process incredibly tedious. I am spending far too much time 
> profiling,
> > and not enough time creating and printing images :( Hoping this 
> will
> > change ...
> > 
> > --- In QuadtoneRIP@yahoogroups.com, Terence Lowe <televe@> wrote:
> > >
> > > I, too struggled with the QTR linearization process.  My approach
> > was to 
> > > try to get the best density measurements by modifying the ink 
> setup and 
> > > grey curve tabs, but with the linearization array clear.  This 
> took
> > many 
> > > iterations.  Eventually, when I thought that the measured 
> density curve 
> > > was close to the ideal density curve (I plotted both in Excel 
> for 
> > > comparison purposes), I linearized, printed the step tablet 
> again and 
> > > checked the new, linearized density measurements to confirm (or 
> > > otherwise) that my final curve was good enough.
> > > 
> > > I made the assumption that it was incorrect to re-linearize the 
> > > linearized curve during the many iterations and so only 
> linearized once 
> > > as the final step in curve creation..  I hope this was the 
> correct 
> > > assumption.
> > > 
> > > Cheers,
> > > 
> > > Terence Lowe.
> > >
> >
>