Re: Epson 2200 inks
Re: Epson 2200 inks
- Subject: Re: Epson 2200 inks
- From: Roger Breton <email@hidden>
- Date: Thu, 15 Jan 2004 16:25:52 -0500
I wrote:
>
> OF course, I don't suppose that there exist some objective CIE agreed-upon
>
> method or procedure to measure and predict the extent of illuminant
>
> metamerism in a paper/ink combination.
To which Robin replied:
>
Remember, illuminant metamerism is what you WANT! It is the phenomenon
>
where two samples with different spectral power distributions look the
>
SAME under two different illuminants! What you guys are talking about is
>
"illuminant metamerism FAILURE".
>
>
There is a CIE procedure for determining a Metamerism Index, Change in
>
Illuminant, which is a measure of how good a set of samples match with a
>
change in illuminant. Check the CIE site for the standard. It is also
>
covered in Berns' book and in Wyczecki and Stiles. See the References
>
section at www.rmimaging.com for the exact reference.
>
>
Robin Myers
As far as I can remember, the many times I followed the discussion of
metamerism here on the this List, especially in the context of Epson's inks,
it's always been my understanding that the appearance of color changes (or
may change) as a function of the illuminant it is viewd under. This, I
agree, is I partly what I think is happening here. I know the RHEM indicator
is a fine example of metamerism. How to explain otherwise the change in
appearance of the pattern when departing from a 5000K light source?
But, I don't think that Illuminant Metamerism is the determining factor here
and neither could the Metamerism Index be used to predict the change in
color appearance. Why? Because, if I am not mistaking, if memory still
serves, to calculate the Index, two illuminants are required. And I don't
think that this is the appropriate test to use to evaluate the extent of
color appearance change caused by the inks when viewing prints under a wide
variety of light sources. I have not had the chance to find a worked out
example of what I am about to describe but, essentially, what I believe I'm
after is something called "Color Constancy Index", a CIE metric originally
developped by Robert Hunt, himself, to describe this phenomenon. But it,s
nowhere to be found in writing. What I do remember about this metric is that
it was created purposely created for evaluating the capabilities of a color
to maintain its appearance under a wide range of illuminants. That's very
different for relating the appearance of some object color from one set of
viewing conditions to another. I once read a page about "Color Constancy
Index" in Hunt's Measuring Color book (towards the end) but, for the life of
me, I could never figure out his presentation -- too theoric for me (then).
I did try to search the CIE site and the web many times for references on
Color Constancy index but it still eludes me.
Suggestions?
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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