[From Dick Robertson] (980310.0658CST)
[From Rick Marken (980306.2350)]
Dick Robertson (980306.1825CDT) --
I wonder whether we haven't reached a point where Bill, Rick and
others ought to save some of your posts in a special file called,
"generic refutations," or the like, and when some, "same old issue"
crops up again, hit the reply button and hit Macro A, B, or C, etc.,
as applies and get on with it?
I don't think we'll ever reach that point. I think that the nice
thing about the net is that we can learn from these on-line
discussions (and I have learned a ton from them) in a way that
is impossible from books. I think the discussions on the net,
though often repetitive in overall substance, can address detailed
questions and concerns in a way that is impossible by just pointing
someone to "B:CP p. 34" or "LCS, p 56", etc.
Maybe, but I can't help wondering what you would be doing instead, if you
weren't addressing the same old question for the nth time. I wonder if it
might not be adding more to the long run development of PCT research?
Anyway, I am really glad to see that your paper (with David) will be
published in the IJHMS issue that Martin is editing. I would like to
see a copy as soon as possible (maybe you could e-mail me an
electronic version?)
Well, I would be glad to post a version on the net, if it's OK with Martin. I
don't know what the protocal is for pieces that have been accepted for
publication. If public postings are not OK maybe a private one would be?
Best, Dick RobertsonFrom ???@??? Tue Mar 10 13:33:48 1998
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···
Date: Tue, 10 Mar 1998 08:22:50 -0700
Reply-To: "Control Systems Group Network (CSGnet)"
From: Bill Powers <powers_w@FRONTIER.NET>
Subject: Re: Physical reality and perception
To: Multiple recipients of list CSGNET
<CSGNET@POSTOFFICE.CSO.UIUC.EDU>
In-Reply-To: <199803100726.IAA05809@glandasse.imag.fr>
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[From Bill Powers (98010.0757 MST)]
Oded Maler (980310)--
Re: objectivity of color.
Just an anecdote, I visited last year a factory for industrial colors
and they showed me how their quality assurance works. You have pieces
of plastic with all the standard colors + catalogs saying what
a spectrometer should show for each of them. They take samples from
various parts of the color container and compare their spectra to it.
The objective agreement is needed here due to the contract between
the client and the manufacturer.
This is a good way to reproduce the collection of wavelengths that
constitute the _stimulus_. If the spectra could be reproduced in detail
(same plot of intensity versus wavelength), then presumably all people
would agree that the sample is the same color as the standard, if both were
viewed under the same lighting conditions, painted with the same thickness
on the same substrate, dried to the same degree, and of the same age.
Note that in order to achieve "objectivity", it's necessary to get as close
as possible to a Level One perception: intensity.
The spectrometer is a first-order perceptual input function that provides
an array of linear intensity measurements sorted by wavelength. The visual
system, however, is a set of multiple-level nonlinear input functions which
represent color through a complex function that involves normalizing colors
over the visual field and computing color-signals for one area of the field
that are functions not only of wavelength but of the perceived colors of
other areas of the field.
Thus when someone brings a sample of a painted surface to the store and
compares it with a plastic chip guaranteed to match the color in the paint
can, the paint may still fail to match the color on the wall at home. The
customer doing the comparison is not a spectrometer; the sameness is being
judged by receptors with a different spectral sensitivity in terms of
wavelengths, under different lighting conditions from those at home and in
the factory, and using a sample of the home color that is composed of
different pigments on different substrates and with different histories of
oxidation and ultraviolet degradation.
The departure from objectivity starts as soon as a living system's
perceptions are used instead of a spectrometer.
Best,
Bill P.'