QTR-Quadtone RIP

Hi Paul,

Thanks a lot for your answer, I think I am getting closer, but I still have
some questions. In particular concerning the RGB channels of the curve.
(See below)

On 2 August 2013 05:09, Paul Roark <roark.paul@...> wrote:

> **
>
> For general information about the inkset, see
> http://www.paulroark.com/BW-Info/UT-3D_Readme.pdf.
>
> Thanks, I had already read this already

>
> I have tried to create ICC curves using the QTR create ICC profile script,
> >
> Use Create ICC-RGB. It allows you to drop a Photoshop image adjustement
> curve into the ICC as well as the linearization data. See
> http://www.paulroark.com/BW-Info/Embedding_Photoshop_Curves_in_ICCs.pdf
>
>
Yes I meant to say the ICC-RGB script.

One question, embedding the Photoshop curve, will I still be able to use
the ICC profile to print from any software, or will this become a Photoshop
only ICC?


> ... my blacks seem to saturate off at about the 85% mark, ...
> >
> You can control that with the PS curve you embed in the ICC or with a
> profile you make for QTR. If the 21-step with no curve hit its dmax at
> 85%, then have a curve that ends at 85% on the black end of the curve.
> Then look at where the inks are and how the R, G and B curves will affect
> the C, M and Y inks. That will give you the control you need. Start with
> the 50% patch and points on the curves at that input level. When you get
> the 50% tone right, go to the 25% and 75% points. It's a iterative process
> (aka trial and error, but you'll probably get the hang of it after a few
> moves).
>
>
So the process would be the following.

1. Create a curve where the black endpoints end at 85%, that is the curve
is still linear (less steep curve), but black ends at the 85% level

2. Reprint the 21-Step wedge using Photoshop, thereby applying the curve to
reduce, the ink output at the high end.

3. Remeasure with the spectrometer and use the output from the spectrometer
+ the applied curve to create a ICC?

This will cause a problem, as now with CS6, Photoshop (at least on the Mac)
will not allow to print anything unmanaged. I will have to assign a colour
profile. This defeats the process. Since Adobe is aware that you will want
to print targets unmanaged, they have created a small app called "Adobe
Printer Utility", which takes a tiff and prints it unmanged. But this app
will not apply the curve. The only thing which might work is to take the
21-Step, apply the curve and save a copy thereby preventing it from
applying a profile. Then use the utility to print out the "new" target and
redo the measurement.


Once I have the black sorted out, I would have to sort out the RGB
channels. What I have not quite understood,  what do I do with the colour
channels? Do I measure the a* b* values and try to minimize them, or what
is the aim here? So I would start to would take the 50% patch, measure it's
Lab values, before and after applying the curve and then try to move the
RGB part of the curve to make them as close as they were before, or as
close to zero, or as close as possible to the a*, b*  values white patch?




> (Because I'm Windows, I'm not going to get into QTR profiling on a Mac, and
> the color management issues may be different.)
>
Paul
> www.PaulRoark.com
>
>
>

Thanks again!

Andrew

-- 
Andrew Maier PhD, PMP
tel: +41 79 34 19 492
email: andrew@...
linkedin: http://ch.linkedin.com/in/andrewmaier


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