QTR-Quadtone RIP

jr,

Thanks for your detailed post.  No, I am not getting banding in the 
initial 21-step wedges for the individual inks during calibration 
mode.  I am getting banding on the 21step.tif file that is printed 
out after you take QTRgui out of calibration mode.  This is the step 
wedge that I need to measure in order to linearize the curve.

This is also not the type of banding you see with a clogged nozzle.  
I check my nozzles before and after each calibration print to verify 
that I didn't have a clog during the calibration print.  The banding 
I'm talking about is not the fine line banding that is typical with a 
missing nozzle.  These are gradient bands (if that description makes 
any sense) that seem like they would be due to improper overlap 
(partitioning) of the 6 inks upon printout.  These gradient bands are 
obvious in the smooth gradient that runs across the top of the step 
wedge.  The bands extend down into the 5% blocks and it seems would 
have an impact on the measuring of the 5% blocks for linearization.

But I will read through your description and cross check against my 
process.

Mike

--- In QuadtoneRIP@yahoogroups.com, "Jeff Randall" <jrandall@...> 
wrote:
>
> Mike:  
> 
> I assume you see the banding in the calibration print stepwedges. 
Do 
> you see banding in just one ink's wedge or in all wedges? Banding 
is 
> usually caused either by clogs, dirty underside of printhead, 
> airleaks, or incomplete purging of old inks associated with the 
> particular ink step-wedge.  Banding in all wedges is often a 
> stepping motor/paper advance problem.  
> 
> I have found that I get better results *generally* following Tom 
> Moore's procedure than Paul Roark's. YMMV! [Desclaimer:  The last 
> inkset I profiled was Paul Roark's K4+Ccm--I have no experience 
with 
> Cone inks.]  If I had your first calibration print at 100%, I'd set 
> the K default limit to something between 50% and 80%, maybe 65 or 
> 75%--I'd have to see the results.   Then I'd print out the second 
> calibration print at what ever % I decided on to make the second 
> calibration print and calculate the relative ink densities to K at 
> that % leaving the limits of the other grays blank and set Black 
> Boost to something like 85% or 90%.  I'd also set the Gray Curves 
> tab values to something like 6,6,_,1.  This will darken the 
> resulting stepwedge below that created by the default values, but 
as 
> Paul says it helps smooth the transition between the 95 and 100% 
> steps and it linearizes well for me.  This would become my base 
> profile.  I'd print out a 21-step wedge and use my 
> densitometer/colorimeter to measure the density or Lab L and plot 
> against the step number or % value. The result should be a smooth 
> curve below the straight line connecting the 0 and 100 readings 
(see 
> Paul Roark's figure).  I then would adjust ink limits as needed to 
> get a smooth curve (for me it usually is the darkest gray I need to 
> tweak the most).
> 
> Hope this helps.  There are no hard and fast rules.  Creating 
> profiles from scratch still has a strong component of art ...
> 
> jr
> 
> 
> 
> 
> --- In QuadtoneRIP@yahoogroups.com, "Mike Dawson" <dawsonm@> 
> wrote:
> >
> > 
> > Can anyone give me some common causes of banding in the step 
> wedge?  
> 
> 
> > With the 1280/K6/Epson VFA combination I found that the ink limit 
> for 
> > the Black ink was at 80%.  The density shoulder actually begins 
> > occuring at about 50% with a density of 1.62.  It hits 1.69 at 
80% 
> > and holds that value up until 100%.
> > 
> > I then printed out the ink separation test using an ink limit of 
> > 85%.  I then determined the densities (compared to Black) of all 
> the 
> > other inks from the 100% squares.
> > 
> > I also measured all ink patches from the first ink separation 
> test.  
> > Based on advice from Paul Roarke I used the ink limits from these 
> > measurements to plug into the curve creation windows.  I found 
> that 
> > ALL of the inks (except for Black) had no plateau and were 
> increasing 
> > in density all the way up to 100%.  So I plugged in 100% ink 
limit 
> > for all the inks, except for Black which has the default of 80%.  
> > Black Boost was left blank.
>