QTR-Quadtone RIP

Hi there,

After a week of ploughing through archives and documentation, it seems 
to me that the art of initial curve creation is one of the best kept 
secrets of QTR. The closest most tutorials get is "yes, it can be done, 
but we recommend you start with a reasonably close profile and tweak 
it". Paul repeatedly told us how his initial curves were hand-drawn, and 
I wonder if this is really the only and optimal method, and if it is, I 
haven't found detailed instructions on how to do this most efficiently.

What I am after right now, is to print the best possible B&W one can 
with the original Claria inks and a 1400. Paul's "B&W Printing with 
Epson 1400 and Claria Inks" seems to be the way I want to go. Printing a 
few 21 step wedges showed me that his profiles needed some tweaking to 
be used on my paper of preference (Harman Gloss Baryta), since there 
were several tone shifts throughout the wedge. Furthermore, I would like 
to create several profiles (to be combined in QTR) like neutral, cool, 
warm, and sepia, all based on BO with additional LM, LC and Yellow.

I thus am looking for a full understanding of QTR's inner life (e.g. 
I've seen the parameter GRAPH_CURVE take the value YES although the 
profile didn't contain any curve description...??), so as to be able to 
start from scratch. I would be highly grateful to anybody pointing me to 
the documentation answering the following questions and help me go further:

- Is there an alternative to drawing the points of an initial curve 
manually?

- Is there a way to automate the correction of LM/LC/Y-curves other than 
by visual/manual trial and error? (I have a Spyder3Print SR at hand.)

- Is there a way to "linearize" a and b values, the way we linearize L 
values by measuring?

Thank you for reading,

Louis

Louis de Stoutz <loudest@...> wrote:

> **
>
>
> ... it seems to me that the art of initial curve creation is one of the
> best kept
> secrets of QTR. ...
>

See http://www.paulroark.com/BW-Info/Eboni-4-Plus.pdf at page 11 et seq.
 That is probably the most stripped down, hopefully easiest to understand
write-up I've made.  This is for a dedicated B&W inkset, however, not a
color inkset (which is the worst case).

... Paul repeatedly told us how his initial curves were hand-drawn,...
>

Not really.  I use the QTR partitioning system whenever I can.  You're just
targeting the worst case scenario -- trying to get a B&W print from a color
inkset.


> What I am after right now, is to print the best possible B&W one can
> with the original Claria inks and a 1400. Paul's "B&W Printing with
> Epson 1400 and Claria Inks" seems to be the way I want to go.
>
http://www.paulroark.com/BW-Info/1400-Claria-BW.pdf


Printing a
> few 21 step wedges showed me that his profiles needed some tweaking to
> be used on my paper of preference (Harman Gloss Baryta), since there
> were several tone shifts throughout the wedge. Furthermore, I would like
> to create several profiles (to be combined in QTR) like neutral, cool,
> warm, and sepia, all based on BO with additional LM, LC and Yellow.
>

As noted above, you're starting with the most difficult case here.  Recall
that the reason the dedicated B&W inksets exist is that it's very difficult
to get a B&W print from a color inkset.  With the 1400, it's small 1.5 pl
drop at least allows us to use a BO curve to hold down the inevitable
artifacts that result from making a B&W print from color inks.  So, the
"best" B&W I've been able to achieve with a color inkset is the "half
color" QTR profiles with Claria in the 1400.  Still, when I need really
good dye B&W from the 1400, I pull the color and put in the 2k2LK approach
carts.  See http://www.paulroark.com/BW-Info/1400-Claria-Noritsu-2K2LK.pdf
Since the 1400 allows mixing Epson and MIS carts, this means pulling 3
carts and doing 2 cleaning cycles.  (Now that I have a 4000 set up with
Epson-Noritsu [Claria type] inks, I'll probably use it most of the time for
B&W dye printing.  See
http://www.paulroark.com/BW-Info/4000-Noritsu-5K-Plus.pdf )



> ...
> - Is there a way to automate the correction of LM/LC/Y-curves other than
> by visual/manual trial and error? (I have a Spyder3Print SR at hand.)
>
> Not that I am aware of.

One thing that I might recommend is that instead of working with a "half
color" profile you make a straight black only profile first.  Then use only
the LM to get that to relatively neutral.  See, for example, my
Claria-BO-RR-Metallic-LM-05 profile.  That profile uses no hand drawn
curves and makes a fairly neutral print.

Once that is done, then I'd modify the "Claria-RR-Metallic-gray" curve for
the paper you're targeting   There is no easy, automatic way to do this.
 Having the "color circle" firmly in mind as you move the points on the
curves is the best you can do.  LM v LC will control Lab A, and Y v. (LM &
LC) will control Lab B.  Once you've done a few points, you'll get a handle
on how much to change them.

At any rate, once this curve is as close as your patience is going to
allow, use the QTR sliders to blend the curves to make a half BO, half
"color-gray" combined profile.

Using the sliders is probably easier than trying to do it all in a single
profile, in part, because the colors errors will be more pronounced in the
full color profile than in a single, half BO profile.

Good luck.

Paul
www.PaulRoark.com


[Non-text portions of this message have been removed]

Thank you, Paul, for your once more very thorough answer! I now am 
confident that I didn't miss out on something lying around readily 
available and am going to brace myself for a round or two of hard work :-)

Louis


P.S. what does that GRAPH_CURVE parameter really do?

This one is pretty easy: with GRAPH_CURVE=YES, the curve generation program outputs a simple representation of the curves, using ASCII characters, in the terminal window, at least on the MAC.

Davud 

--- In QuadtoneRIP@yahoogroups.com, Louis de Stoutz  wrote:

>
> Thank you, Paul, for your once more very thorough answer! I now am 
> confident that I didn't miss out on something lying around readily 
> available and am going to brace myself for a round or two of hard work :-)
> 
> Louis
> 
> 
> P.S. what does that GRAPH_CURVE parameter really do?
>