Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "David Whistance"
<david.whistance@...> wrote:
>
> Tyler
> 
> Many thanks for your advice.  It looks as though the solution may be to
> substitute an Eboni cartridge, however you have me intrigued.

I was afraid of that <G>.

>  What would
> you generally use underprinting for if it is not to increase Dmax? 

Reasons differ for color or mono inksets. For straight color using a
RIP and CMYK profiles the black point is generally a "build" of CMYK,
and the differences we are seeing here are well worth the efforts over
the RGB driver.

For mono inkets it's very different. Obvioulsy one main reason would
be to investigate a better black dmax as you know. Another may be
longevity. If the K ink changes more than the others, underprinting it
 or "protecting" it with another stable dark gray changes the
longevity characterristics of the black point in the prints, since
it's a build. Another reason may simply be visual, not everything is
determined by specs and it's possible a tinted ink thrown in with the
K may simply make a more beautful print.
Or, none of these things may result, it's a matter of playing around.

> How
> would you generally underprint?

With StudioPrint it's not as flexibale as I would like. In a mono
environment I simply assign another tank to K along with the actual K
ink. Porportions are not user selectable, though layered vrs
distributed dots are.
I don't use K7s, but a dual quad set, so I often have an unused dark
gray ink to utilize. If they are both already in use, there are other
tricks...

>  I am not sure whether this information will
> be of use for either of the RIP's that I use; QTR and Bowhaus OPM,
however
> it might be helpful in future.

I don't know how it may be done with QTR. In some tests long ago it
seemed to be done with the overlap control, but I was frustrated by
the increased dots in other parts of the scale since it's applied
everywhere, not just K. Clearly that control was designed for other
purposes.
With Bowhaus I believe you can literally draw any curve you like with
any ink. In that case I would probably just leave some of the dark
gray in at 100% instead of pulling it all out under the K. That's what
we used to do many years ago making our own partitioning curves and
printing through PressReady in CMYK with a quad set. Many tests were
done to find the best dmax trying different percenatages of K and the
darkest gray. With thse old inks it was usually about 99%K and 75%
dark gray if I recall. Depends on the paper as well of course.
Hope that helps.
Tyler