Geometry is the Basis for the Color Constancy of Vision!

A definition from Wikipedia of the unique color constancy of the vision process”

“Color constancy is an example of subjective constancy and a feature of the human color perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions. A green apple for instance looks green to us at midday, when the main illumination is white sunlight, and also at sunset, when the main illumination is red. This helps us identify objects.”

In striking contrast, color photography does not possess this characteristic where the color of an object is not constant but is altered by changing ambient illumination. Color photography requires that filters be used to correct for this effect and render the object of interest close to its’ “true” color.

The vision process possesses color constancy. Color photography does not.

I have written proposing an explanation for this visual characteristic and the reader is referred to Comment of March 3, 2006 on this subject.

Clarifying those thoughts – it follows from Osterberg’s historic retinal morphology measurements and the antenna premise of this work that the exact mid-band point of the visual band (i.e., 550 nanometer) is geometrically-defined on the retinal surface at an eccentricity of between seven and eight degrees. This corresponds to the eccentricity where sufficient rods are present in the retinal motif to completely surround each cone (Osterberg’s data and figures). This provides the fixed reference that Land termed a “fulcrum” from which all other wavelengths of the visual image are compared to produce the hues of “color”. I propose that this fixed wavelength reference provides a basis for explaining the color constancy of the vision process.

I would add that this precise location defines the peak intensity of 550 nm midband wavelength radiation being the location of the maximum density of optical interactive antennas (cone-rod appositions) on the retinal surface. It is the intensity distribution across this band (and across the other cone-cone and rod-rod bands) that Land termed “lightnesses” compared by vision to create the hues of color.

As I have noted, these wavelengths are indeed “primary” but they do yet represent “color”.

Fundamental geometry!

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SUGGESTION FOR INVESTIGATION:

Check the validity of my statement that the 550 nanometer wavelength falls on the retina at an eccentricity of between seven and eight degrees. In a very preliminary effort using LIGHT TOOLS software (Optical Research Associates, Pasadena, CA), and entering the optical parameters of the structures of the eye , it very quickly becomes apparent that this wavelength is incident on the retina at this eccentricity. Subsequent to this effort, I visited with an individual in vision studies who had generated a far more comprehensive simulation than mine (I believe directed to support of the LASIK procedure). I do not feel able to quote this individual as he said that he had not published the data. In any event his simulation showed that 550 nm interacted at precisely the 7-8 degree eccentricity point on the retina. Someone should follow this up!

5/2/08