EDWIN LAND’S THEORY OF COLOR VISION

by Gerald Huth on May 5, 2010

PREFACE

It occurs to me that many readers may not remember Edwin Land’s work on color vision and particularly his seemingly amazing experiments that appeared in the 1950’s. In the ensuing sixty years these experiments have been persistently ignored by vision science to the point where I wonder how many of the younger generation have even heard of them?

If one is not offended by the popularization of scientific endeavors, one might see in Scientific American of May 1959, “Experiments in Color Vision” by Edwin Land (a figure from this article even made the cover). Shortly after the appearance of this article, kits of negatives etc to perform these experiments were even made available by Edmunds Scientific Corp.

Additionally, Land published a great many papers on this subject in scientific journals. An example: “Color Vision and the Natural Image”, Edwin Land, Proc.of the National Academy of Sciences, Vol. 45, No.1, January 1959. Land was a true scientist and not just an “inventor” the term often used in characterizing him!

Also in this context I remember a beautiful 1985 BBC documentary titled “Colourful Notions” where Land demonstrates his color vision experiments. This is well worth viewing.

TEXT OF THIS COMMENT

Following the previous Comments, I want to be clear as to how this view of light detection on the retina precisely defines the mechanisms within the eye that explain Edwin Land’s theory of color vision – results that he so presciently deduced over sixty years ago from measurements made external to the eye.

First, as always, the reader must free herself or himself from the totally mistaken beliefs of the past on the subject of light interaction with the retina!

So,

1. The image encoded by the all-cone foveal region provides Land’s “long wavelength record”. This is a totally monochromatic image that is the analogue of the black and white photographic image used by Land.  ( and, as I have often pointed out this also defines the exact ( not almost) long wavelength limit of the visual band)

2. As found uniquely in this work, the exact midpoint of the visual band is geometrically encoded at 7-8 degrees of retinal angle by the completely octagonal symmetry of rods-around-cones on the retinal surface. This corresponds to the central wavelength “fulcrum” that Land found must be present. THE EYE USES GEOMETRY TO ENCODE WAVELENGTH.

3. The image encoded by the predominantly rod-containing region to ~ 20 degrees encodes Land’s “short wavelength record”. This again is a monochromatic image and is the analogue of the black and white photographic image used by Land ( the rod-rod appositions provide the exact short wavelength limit of visual response).

These are precisely the three elements that Land saw necessary to effect or synthesize the hues that we term color.

The only thing further to be added is to realize that all of this occurs within the near field of the light wave (i.e., at spatial dimensions of less than one micron) and in the fast tme domain approximating femtoseconds (10-15 sec.)

GCH

Ojai,CA

5.05.10

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