QTR-Quadtone RIP

Mike, are you using the Ordered dither algorithm? If not try switching 
to that.

Howard

Mike Dawson wrote:
> 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.
>>
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
> 

-- 
Howard Shaw
glassman@...
www.howardshaw.org