RE: Metamerism

From: Rocky J. Boudreaux ^lt;>
Date: 04/19/04-03:55:00 PM Z
Message-id: <>

OK - But, like how far out on the horizon ?
It would be great not to have to build special profiles etc.
What's the chance they will be Epson rather then after market?

Houston, TX

-----Original Message-----
From: Editor P.O.V. Image Service []
Sent: Monday, April 19, 2004 1:51 PM
Subject: Re: Metamerism

Judy Seigel wrote:

Thanks Bill -- very interesting and for whatever reason more info on the
topic than on the long-ago Epson list, or anyway new info. Now, however,
since you know so much -- why is this suddenly such an issue? Are inkjet
inks more metamerism-prone than other colors ?I'm not Bill, but I'll answer

Yes and no..

The color pigments currently used in pigment-based inksets are, in many
cases, encapsulated in epoxy resins. The encapsulation increases the
metameric properties of some of the pigment particles. In other cases, the
pigments themselves tend to be metameric. Part of this is the physical
nature of a pigment when compared to a dye. The pigment has a physical size
and nature that actually reflects light differentially, whereas a dye simply
works by additively coloring the media, without changing the physical
reflectivity substantially. Additionally, the refractive qualities of the
epoxy encapsulation can increase the metamerism at select wavelengths - as
the refraction of light passing through the epoxy differs by wavelength.

One of the most metameric traditional pigments is Cobalt Blue. Take a photo
of a gorgeous oil that utilizes Cobalt Blue, and almost invariably it
appears purplish. This is because the cobalt blue converts near IR light
reflected onto it to a more visible magenta tone, so when scanning or
photographing artwork incorporating cobalt blue pigments, one needs to block
as much IR light as possible from falling onto the artwork. Or.. if the
image is captured via a digital process, one should also block as much
reflected near IR as possible by adding a blocking/hot-mirror filter, as
digital capture has heightened sensitivity to IR than does the human eye.
There is a whitepaper on this on the BetterLight website, explaining all the
work that has gone into simply allowing BetterLight digital backs to
properly image artwork containing cobalt blue pigments.

The problem with dyes is that they tend to be more fugitive, so OEMs have
moved towards pigments.. Pigments are more stable but they bring their own

All that said, as the newer generations of pigments come out, like the
Ultrachrome HG inks in the R800, and as pigment capsule and particle
combination sizes drop substantially, metamerism is decreasing as a result
of both physical factors and pigments that are themselves less metameric in
the first place..

  In printmaking, color
photography, painting & drawing, etc., you knew colors looked different in
different lights, but it didn't seem to be such an issue. Is metamerism
worse, or more uneven, in inkjet?
  It's just a fact of newer pigments and ink formulations.. Oils, litho,
and traditional printmaking evolved over much longer timespans... So, the
bad boys were weeded out.. Problematic inkjet pigments are being weeded out,
and new ones developed quickly, but it takes time..

As an aside, there are dye-based inksets on the VERY near horizon that have
archival qualities similar to the best of the current pigments. The
dye-based nature of these inks avoids many of the problems inherent in
pigment-based inksets.

Keith Krebs
"Just some guy," caretaker of the Multiverse's largest EPSON printer User
Community (highly recommended by Vogon Poets and MegaDodo Publications), at:
and  the Multiverse's largest Canon printer User  Community at:
"For the rest of you out there, the secret is to bang the rocks together

Received on Mon Apr 19 15:55:41 2004

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