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Re: Color constancy



I understand there is evidence that our visual system does some processing
before things get to the brain. Part of this processing either in the
retina or in the brain involves an edge enhancing effect which tends to
heighten the contrast in the "vicinity" of a sudden change in what
individual cells in the retina "see". This happens in the very early
stages of processing signals from and in the retina. I'm wondering if the
sensation of the "halo" of a different (contrasting) color isn't due to
this.

Perhaps we could call this the Hendrix effect ;^)?

Dewey


I see the haze with and without glasses - so do my students. If I had to
guess, looking at the orange directly overwhelms the very faint
perception of color. I wonder if all of us perceive a UV source the
same.

Scott



Date: Thu, 2 Nov 2000 15:29:08 -0500
From: Robert A Cohen <bbq@ESU.EDU>
Subject: Re: Color constancy

Why is the purple haze *around* the orange instead of coincident with it?

My first impression was that only those with glasses would be able to see
the purple haze (due to dispersion through the glasses) but I had assumed
the colors would be coincident.

----------------------------------------------------------
| Robert Cohen Department of Physics |

On Thu, 2 Nov 2000, S.Goelzer wrote:

Also, on the subject of color perception, when I show a one of the plasma
flower
light bulbs* some students can see a faint purple haze around the orange
plasma and
others cannot. I think this maybe the result of being able to perceive
color deeper
into the UV.


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Dewey I. Dykstra, Jr. Phone: (208)426-3105
Professor of Physics Dept: (208)426-3775
Department of Physics/MCF421/418 Fax: (208)426-4330
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"As a result of modern research in physics, the ambition and hope,
still cherished by most authorities of the last century, that physical
science could offer a photographic picture and true image of reality
had to be abandoned." --M. Jammer in Concepts of Force, 1957.

"If what we regard as real depends on our theory, how can we make
reality the basis of our philosophy? ...But we cannot distinguish
what is real about the universe without a theory...it makes no sense
to ask if it corresponds to reality, because we do not know what
reality is independent of a theory."--S. Hawking in Black Holes
and Baby Universes, 1993.
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