QTR-Quadtone RIP

--- In QuadtoneRIP@yahoogroups.com, "milogiacomorambaldi47"
<milogiacomorambaldi47@...> wrote:
>
> I'm still looking for heuristics for selecting the best Default Ink
> Limit.  This seems to be an important first step, but the best
> approach seems unclear.
> 

Milo (?), I don't know about heuristics but this is what I do.
When the transitions on the initial 100% calibration print cease to be
at least 0.03 density ( or approx 0.075 Lab L*), I select that or the
previous step as the default limit and reprint the calibration chart
with it. For me, doing it that way has always prevented the error
problems in linearizing the curve later on. If you have the
measurement tool, I would use it's #s rather than visual estimates.

> 
> "Reprinting the ink separation page, limited to 50 this time, I could
> see PK transitions up to 75 - but no further. 

You can leave all inks at the default limit ie: don't put any value
into the separate limit boxes for each ink, but you don't have to. You
can use different limits for each ink. Whatever you put in those boxes
will over ride the default, is my understanding. I don't know if
limiting the lighter inks a lot more than the default will impact
smoothness of results or not but I think it is likely that it would.

What I am wondering is why you aren't seeing transitions farther up
the scale with the PK. Where was it on the initial 100% limit
calibration print? I would be tempted to limit it a bit more than the
default for K until it transitions better or just lower the default
limit a bit more.
> 
  Regardless of
> whether I set Black Boost to 55, 60, or 100...
> 

Roy has stated several times that you should not use more than 110 to
 115% of default limit for your boost value. As you have noted it only
is supposed to impact maximum K ink.

>
> Two questions:
> 
> 1.  Do matte papers typically exhibit this behavior compared to
> glossy?  I've only done one of each, so I really don't know.
> 
> 2.  What about the Gray Curve tab?  So far, I've always left Highlight
> = Shadow = 6.  Is it worth increasing Black Boost (even to 100) to
> regain dMax and then increasing Shadow (10? 20?) to lighten the bottom
> transitions?
>

Papers can and do vary quite significantly for both types.

I would first get a good feel for what is needed with regard to
limits,boost and the relative densities of the K & LK inks before
adding more variables to the equation. See that overlap is 0 to keep
d'max as high as possible also. After you have a nicely transitioned
21 step scale and can linearize it without trouble, is the time to go
back and play with the different variables to see what they actually
do IMHO.

Regards,
Duane