QTR-Quadtone RIP

Howard.....a little feedback.  I ran both tests you suggested.  

I found that using BO in my profile did give me the same Dmax as I 
originally got in the MK step wedge when printing the original 
inkseparation file.  In this test, I printed on Red River Aurora 
Natural paper, and hit a Dmax of 1.65 on my 4000 at 85% ink.  I got 
this on the inkseparation target and a BO profile using only the MK 
with an 85% ink limit.  (This is using the MISPro color inkset - UC 
equivalents).

I also tried the counterintuitive move in increasing the overlap of 
the lighter inks (it was originally set to 0).  I tried an overlap of 
10 and 20.  They both slightly reduced the Dmax to about 1.63, but 
that was less loss than I anticipated.  The neutral profile I built 
had LK, LC and LM inks for neutrality and smoothness in the light 
tones.

This leads me to conclude that the addition of light inks into the 
shadows is, in fact, slightly reducing Dmax in most of my profiles.  
I don't see a way of completely eliminating this using the normal 
tools in QTR's Gray Ink tab.  You can minimize it by moving the 
Shadow field in the Gray Curve Tab to a lower number (closer to 
zero), which limits the use of light inks in the shadows.  To 
completely eliminate light inks in the last step of the step wedge, 
I'd probably have to create a plot list or import a curve from PS 
(which may be my next experiment).  

I also think Paul Roark's comment may be part of the explanation 
too.  Since I tweak a profile by repeatedly sending the same sheet of 
paper through the printer, (printing the 21 step random test target), 
perhaps wheel marks are having some impact and skewing readings.  
Also, I use the microwave for 12-15 seconds after each test strip is 
printed, and perhaps the repeated use of the microwave has some 
impact on paper moisture, ink receptivity, or something.  Not sure 
about those, but I do feel reasonably confident after these tests 
that light inks are most most of the reason for a loss of 0.03 to 
0.05 Dmax in the deep shadows.  

Lou


--- In QuadtoneRIP@yahoogroups.com, "Louis Dina" <lou@...> wrote:
>
> Howard,
> 
> Good point.  I will try both.  I am guessing that increasing the 
> overlap will hurt rather than help, but you never know until you 
try 
> it.  The black only curve should make it clear whether the light 
inks 
> are the culprit or not.  If I get the same Dmax in a BO profile as 
I 
> do when I print the inkseparation target, that would seem to 
confirm 
> it.  If not, then something else is at play here.
> 
> Regards, Lou
> 
> --- In QuadtoneRIP@yahoogroups.com, Howard Shaw <glassman@> wrote:
> >
> > Louis Dina wrote:
> >  >
> > > 
> > > All my profiles have the overlap set to 0.  I agree, the black 
> boost 
> > > SHOULD replicate what I got on the calibration target, but it 
> > > doesn't.  The final profile always has a Dmax that is lighter 
by 
> 0.03 
> > > ...
> > 
> > Perversely then, I might suggest that you try a positive figure, 
> say 
> > 10-20, for the overlap.
> > 
> > Also, for testing purposes you could try a black only curve - 
that 
> would 
> > confirm or eliminate the LK as being the problem.
> > 
> > Howard
> >
>