QTR-Quadtone RIP

Olivier wrote:
>  
>>> I'm sure that David has nice automatic equipment that may 
>>> read the targets patch wise and he started making his 
>>> excellent profiles for Epson 9600's with some support from 
>>> Epson (read: well calibrated printers). Not linearising with 
>>> a  manual Spectrocam the customised Epson 9000 made for dye 
>>> inks loaded with third party quad inks :-)
>> Busy day yesterday. Bill its should be.
> 
> Ernst, the idea of multiple linearizations is different from tracking 
> printer instabilities and/or reading errors. Your points are all 
> valid but imho do not tackled the issue I'm referring to.
> Linearization is a simple function where you simply swap input-output 
> values and get the corrections needed. With a single chanel output, 
> probability is high that this simple function will achieve the aim. 
> Now with ink split curves and overlaps, I doubt the function remains 
> that simple because it's my understanding there's no simple model of 
> reversing multiple density outputs due to dot gain, light scaterring, 
> overlapping, etc... So sampling iterative adjustments is the best 
> option to optimize the output untill you reach the point of tracking 
> noise. This is the way linearization is proceeded in commercial 
> packages such as Studioprint and this is also what I have experienced 
> with QTR : once the output is linearized even on a 51stepwedge I 
> don't get a clean linear scale with error above dE 2, read with a 
> DTP41 uv-cut in Colorport. Alternative readings with a DTP20-
> ColorShop (aka Pulse) deliver the same results and multiple readings 
> remain in a dE 0.5 acceptable range after proper drying time.
> 
> Anyway, I agree with you that a proper calibration and in the quad 
> case, a proper ink split curve shaping is critical. At the time being 
> this is my depressing concern, far ahead linearization. I know 
> there's a computation to do it but I don't know which. 
> 
> Olivier

I know it is a different approach. Maybe because I started 
with more mediocre equipment that I'm more skeptic about 
consistency in the total linearisation method and used 
multiple targets + measurement averaging as the better 
option for my system. On the other hand I did the 
partitioning good at that time and got nice linear output.

You could have a point that correction on the overlaps may 
not work out as needed but I think the QTR linearisation on 
the partitioned channels total as theoretically better than 
calibrating individual channels and the partitioning done 
after that like happens on my Z3100. It could be compensated 
with an active partitioning in the Z3100 though. And I have 
no reason to complain about the Z3100 results. How 
Studioprint does that I do not know. If QTR's linearisation 
corrects the output in fine enough steps and the printer is 
consistent in its output it should cope with overlaps, 
dotgain etc. If that isn't the case iterative measurements 
will not help either. Of course when iterative measuring is 
implanted in QTR's linearisation this should mean finer 
adjustment on the output if the adjustment was not fine 
enough already. Roy is the one qualified to give an answer 
on that but he was already qualified when he wrote that 
linearisation tool so I guess it must be working correctly.


-- 
Met vriendelijke groeten, Ernst


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