QTR-Quadtone RIP

--- In QuadtoneRIP@yahoogroups.com, "rdpritchard" <rdpritchard@g...> wrote:
> I'm posting this thinking this may be of use to other newbies like me.
> 
> Today was the first time I tried to use QTR to characterize and do 
> curves and got some seemingly strange results.  I'm using the Windows 
> version on an Epson 4000. In doing my Hardware Ink Limit with Moab 
> Kayenta paper, Black maxed at 65% (density = 1.61 with an Eye One 
> spectro) then decreased after that; 100%=1.49. I duplicated results 
> with a second sheet of paper. Checked this on H Photo Rag and Moab 
> Entrada, same pattern of maxing out around 65%, then decreasing.
> Cyan maxed at 95%, Magenta 85%, Yellow 85%, the three light inks at 
> 100%.
> 
> So I have two immediate questions: 
> 1.  Is this non-linear pattern supposed to happen?  
> 2. What should I use for my Ink Limit?  I assume it should be based on 
> the full strength inks, not the light versions, but even with these I 
> get a range from 65%-95%.  Tom Moore's user guide says the the ink 
> limit value is not critical, but which one to use....?
> 
> I used the 65% value and forged on.  My first test with the 21 step 
> tablet showed the same non linear density pattern. Max black (1.60) was 
> 55-65%, density decreased both below and above that range.
> 
> Again, is this supposed to happen or am I doing something wrong.  
> 
> Thanks,
> 
> Bob

Bob,

What you are seeing is not too unusual.  Too much ink does have a tendency
to reduce dMax.  So just use the 65% value, this is a reasonable value for
the 4000.  I.e. use 65 as the ink limit for the inks, less than 65 makes
sense for the inks that are toner inks since you just want less than max color.

Looking at the existing profiles is a good way to start.   In fact I always
start with an existing profile and go from there.

Roy