RE: Dry Time for UltraChrome inks/Calibration
RE: Dry Time for UltraChrome inks/Calibration
- Subject: RE: Dry Time for UltraChrome inks/Calibration
- From: Ray Maxwell <email@hidden>
- Date: Tue, 4 Feb 2003 13:44:41 -0800
Robin Wrote:
>
Be careful here. Looking at increasing saturation on a*b* diagrams (what
>
you are incorrectly calling "spider plots") can lead to false
>
conclusions unless you understand some things about the L*a*b* space.
>
When you plot the a* and b* coordinates of step wedges of the primary colors
and their overprints and connect equal tone steps you get a diagram that
looks like a spider web. Note that I defined my slang terms in my post. If
you have a formal definition of "Spider plots" I would be interested in
hearing it.
>
These areas where color "hooks" around and "changes lightness" are
>
natural "features" of the L*a*b* color space. They may have nothing to
>
do whatsoever with the ink. This is one of the reasons that the L*a*b*
>
was never intended for color matching calculations. It was designed to
>
be used for representing color differences only. There are a number of
>
color science volumes that discuss this and I would invite you to check
>
the reference list on my website for them.
>
>
Robin Myers
>
Please give us the URL of your website. I am interested in seeing it.
Robin you are referring to the very small curves that result when you plot
constant hue in the Lab color space. I understand this and agree with you.
I am referring to a very gross effect produced by some ink and paper
combinations. Unfortunately, we cannot enclose diagrams on this forum.
Plot the following values and you will get some idea of what I am referring
to.
a* b*
0.58, -3.80 (white point of the paper)
-29.96, -43.72
-32.49, -51.91
-30.97, -57.03
-19.67, -61.42
-12.85, -62.01 (100% Cyan)
I have not include all of the points, but I think you can get an idea of
what I mean by hook. This cyan ink and paper combination actually folds
back on itself. I am suggesting that you set the ink limit for this ink
somewhere near the maximum C* point.
Ray
Creo
Ray Maxwell | Senior Color Systems Engineer, Inkjet Printing
4225 Kincaid Street | Phone (604) 451-2700 ext. 2004
Burnaby, B.C.
Canada V5G 4P5
IMAGINE CREATE BELIEVE
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