RE: Maximum Chroma vs. Maximum Gamut
RE: Maximum Chroma vs. Maximum Gamut
- Subject: RE: Maximum Chroma vs. Maximum Gamut
- From: "Richard" <email@hidden>
- Date: Fri, 12 Mar 2004 14:55:52 -0000
-----Original Message-----
From: email@hidden
[
mailto:email@hidden] On Behalf Of James B.
Reswick, Jr.
Sent: 12 March 2004 06:43
To: email@hidden
Subject: RE: Maximum Chroma vs. Maximum Gamut
Hi:
It seems from the responses that the contaminants consist of the other two
primaries. Is it possible that some of the contaminants are colors other
than the two remaining primaries (which as contaminants would make gray),
that might have been used to make the primaries by the ink
manufacturer? In other words, could it be that increasing the ink to
increase the contaminants could actually expand the gamut in those
non-primary contaminant colors?
------------------------------------------------------------------------
Firstly I must dispute your colour definitions.
Printing inks are CYMK and therefore not primaries. They are indeed the
"other" classification.
If a Cyan was perfect it would absorb all the Red light cast upon it, surely
you know that. Because it does not, it then becomes necessary to introduce a
process that I know from my time in the print, as colour correction i.e.
wherever cyan prints with another complimentary there will always be too
much Red reflected. When introduced into a 3 colour mix this is/was known as
the Grey component as it added no colour but did contribute an unwanted
colour which in effect resulted in a sort of neutral darkening or degrading
of a particular other colour or group of other colours.
As ink film thickness is increased on the press the colours become stronger
up to a maximum density which for example on a cyan could be 1.1- 1.5
depending on the ink and paper used. I do not know what the current density
figures would be as I have been retired for eight years.
If ink film thickness was increased above that point then no further
"colour" would be seen because a lot more unwanted colour would contaminate
or degrade the particular ink or inks being printed.
In addition because the density increase is reducing the amount of light
reflecting from the paper base, less light will be available to impress the
eye. In addition because of the amount of non image forming light i.e. that
reflected from both the surface of the print and possibly internal diffuse
non image forming light as well, the eye will perceive a reduction in actual
colour saturation and contrast.
Even though you can colour correct for deficiencies in composites made up
from 3 and 2 colours you cannot alter the amount of any single colour in any
particular printed dot so that for instance where a Magenta hits a Yellow to
form a Red a typical maximum saturation would made 100M+70Y (give or take a
bit), each complimentary is still carrying the unwanted reflections. All you
can do is reduce Y in M (because Y is a far better theoretical reflector
than Magenta but both inks are still reflecting unwanted colours.
There hangs the dilemma of what I know as four colour offset printing and no
doubt Ink jet printing too.
Richard
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