QTR-Quadtone RIP

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.