QTR-Quadtone RIP

Louis Dina wrote:

> It is true that the light inks are at 0 at 100% when overlap is set to 
> 0, but they start coming in right after that.  It seems to be just 
> enough to have some impact on Dmax.  

> Lou

Lou,

Where do you limit black ink itself, right at the point 
where no density increase happens or do you go a bit higher 
where the extra ink shouldn't add more density in theory but 
isn't taking density away either ? I have done the last in 
the past with the idea that some reduction by the 
linearisation curve just below 100% will solve a flat part 
there but a stricter ink limit may loose density in the two 
steps of linearising and profiling and/or fluctuations of 
printer and paper coating. In short a slight bleed to be 
preferred above any white appearing.

On the darkest grey ink running close to the 100% and 
reducing density I think it depends much on how dark that 
grey ink is and how consistent the printer's dot pattern. I 
had my doubts about the HP Z3100 quad use for  some matte 
papers:  MK,PK,Medium Grey and Light Grey where the PK can 
not bridge much of the tonal range so why use it.  But 
before that I used the same configuration in my 9000 MIS 
quad to fill in (to a degree) irregularities of the black 
dot pattern. The same concept that is used in multihead BO 
printing now en vogue. I have no idea how the HP Z3100 B&W 
mode adds the PK in the partitioning but I think it is more 
to deepen the black than for the shadow range. The HP B9180 
doesn't have that quad partitioning but has superb 4800 
lines stepping resolution hardware and 1000 nozzles per head 
so also for the black. Based on that is a superb screening 
resolution and patterns with 16 bit screening masks. No need 
for PK to close the ranks. When Roy made QTR the printers he 
had to work with then could use a bit of overflow from the 
dark grey ink instead of relying on the black only. It may 
not have been intentional but I guess he did work with trial 
and error. No problem, no solution needed. Now with better 
resolution and consistency this may be no longer the case.


-- 
Met vriendelijke groeten, Ernst


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