QTR-Quadtone RIP

lebleur wrote:
...
> 
> Setting the density of the first gray (LK) is pretty clear.  Try to
> match the density in the black (K) step wedge to set the 100% gray
> density as a proportion of the black step wedge.  For the lighter
> gray (LLK) repeat.
> 
The way I do it is to determine where the 100% LLK matches the LK and 
then apply that percentage to the LK to K percentage. For example:

LK 100% matches K 45%
LLK matches LK 30%

Therefore limits:
K 100%
LK 45%
LLK 13.5% (30% x 45)

I'd be interested to hear other methods. To be honest I usually find 
this method gives a slightly too dark end result so I usually end up 
backing off the ink limits a tad to get the unlinearised curve as close 
to optimum as possible.

> The question I have is for the LLK density, does one enter the
> comparative density as read off the K step wedge or the comparative
> density as read off the LK step wedge?  i.e with the K ink density
> set at 100%, the 100% LK density in my test strip was 43% of the K
> step wedge.  The LLK density was 40% as compared to LK and 28 % as
> compared to the K strip.  Which value do I use in the curve creation
> process for the density of LLK (40 or 28)?
> 
Using my method
K 100%
LK 43%
LLK 17.2%

> Also, the UT-R2 inks consist of only three gray inks - K, LK and LLK.
> The R220 is a hextone printer, so the other three cartridges contain
> duplicate inks  i.e.  The cyan and magenta cartridges contain the
> same ink (LK) and the light cyan, light magenta, and yellow all
> contain the LLK density ink.  In setting up the curves, should one
> disable the duplicate ink cartriges, or use the "copy from" method in
> setting their densities and limits?
> 
> 
Yes, you could use Copy curves to duplicate the respective positions. ie 
set magenta to Copy Curve C, etc. On the other hand you could buy the 
UT-R2N set, put the LK & LLK in the M & LM positions and then be able to 
have warm & neutral curves in the printer at the same time. You could 
then even add UT7 sepia or a toner ink of your choice in the Y position.

Howard