Re: Metamerism vs Color Inconstancy, again
Re: Metamerism vs Color Inconstancy, again
- Subject: Re: Metamerism vs Color Inconstancy, again
- From: Jacob Rus <email@hidden>
- Date: Fri, 9 Jul 2010 22:08:53 -0400
Klaus Karcher:
>>> Let us keep in mind that color is first and foremost a
>>> perception and not a physical property.
Marco Ugolini:
>> Whereas I verifiably said otherwise, in my usual "dogmatic" manner. I see.
>> (Where are the quotes to back this up, by the way?)
Klaus Karcher:
> I don't know how this is defined in the English-speaking language area, but
> in Germany we have the industry standard DIN 5033 which defines color
> unambiguously as a human sensation (i.e. not a physical property).
The CIE's definition in the International Lighting Vocabulary is I
think the most widely accepted official technical definition of
"color" and other terms in the field.
According to Mark Fairchild's _Color Appearance Models_ (2005, p. 84),
that definition is:
> Color
> Attribute of visual perception consisting of any combination of chromatic and
> achromatic content. This attribute can be described by chromatic color names
> such as yellow, orange, brown, red, pink, green, blue, purple, etc., or by achro-
> matic color names such as white, gray, black, etc., and qualified by bright,
> dim, light, dark, etc., or by combinations of such names.
Fairchild mentions that the ASTM also publishes definitions of several
color-related terms. I'm not precisely sure what those definitions
are, but I believe that color is there too defined as a perception.
If we want to go back in history a bit, here's the consensus
definition of the Optical Society of America's Committee on
Colorimetry (1944):
> Light is the aspect of radiant energy of which
> a human observer is aware through the visual
> sensations which arise from the stimulation
> of the retina of the eye.
>
> Color consists of the characteristics of light
> other than spatial and temporal inhomoge-
> neities; light being that aspect of radiant energy
> of which a human observer is aware through the
> visual sensations which arise from the stimula-
> tion of the retina of the eye.*
Again, a definition based on perception.
If we go back still further, here's the definition from the Committee
on Colorimetry's report in 1922 (Trolland was the primary author):
> Color is the general name for all sensations arising
> from the activity of the retina of the eye and its attached
> nervous mechanisms, this activity being, in nearly every case in
> the normal individual, a specific response to radiant energy of
> certain wave-lengths and intensities. It may be exemplified
> by an enumeration of characteristic instances, such as red, yel-
> low, blue, black, white, gray, pink, etc.
>
>
> It is imposible [sic] to identify color with radiant energy, or with
> wave-lengths of radiant energy, although radiant energy is the
> adequate stimulus for color. This is because color is known to
> depend upon the presence and character of the perceiving individ-
> ual and because it is directly recognized to be something radically
> different in kind from its stimuli. Consequently, nothing but
> confusion can result from the use of the word "color" as a synonym
> of "wave-length" or "wave-length constitution." Color cannot
> be identified with or reduced to terms of any purely physical con-
> ception; it is fundamentally a psychological category.
This is the primary ancestor, as far as I know, of the later
Colorimetry Committee, ASTM, and CIE definitions (and probably the DIN
definition as well).
There is a lengthy footnote to Trolland's 1922 definition, which
explains that it was the result of a protracted and careful debate
(especially since "color" was often used only for colors with
discernible hue content, excluding grays). Another footnote explains
that:
> The word sensation is used here' to stand for an elementary form of experience
> or consciousness normally depending upon the operation of a sense organ. Although
> the existence of any sensation rests upon the operation of the nervous system, this
> should not lead us to localize it in that system. Although color is not a physical entity,,
> it obviously exists outside of us on the surfaces of objects as we see them, such visual
> objects or perceptions being themselves nothing but arrangements of color areas in
> space. This statement, however, should not be misinterpreted to mean that the colors
> are physical or are located on physical objects. There is no reason for supposing that
> visual objects are identical or coincident with the objects of physical science.
Hopefully that clears things up,
Jacob
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