I was reminded of Edwin Land after seeing his picture in the Business Section of yesterday’s New York Times. When I began this work on vision in 1991 one of the first things I remembered were Land’s anomalous color vision experiments of the 1950’s that derived a full color image from the superposition of two black and white negatives. This strange result even rose to the pinnacle of popular science at the time ascending to the cover of Scientific American (May 1959). Edmund Scientific (for those who will remember!) even sold kits of these negatives so that one could perform this feat at home. I felt certain that in the forty intervening years vision science would have provided an explanation. It became clear, however, that not only had the experiments not been explained but Land’s name had almost completely disappeared from the literature of vision!
In one exchange with a prestigious university group engaged in vision research I was told early on that “the field had put Land’s work to bed years ago” and I was pointed to a paper by Walls with the curious title that shouted “LAND! LAND!”. This paper had been published in Physiological Bulletin (Vol. 57, No. 1, 1960). Incidentally, this reference does not seem to appear associated with Walls’ publications on the web. I dutifully obtained the paper and was distressed to find that it consisted of page after page of ad hominem attacks on Land and his experiments damning him with faint praise as an “inventive genius” (read “not a scientist”). Land’s experiments generated a great deal of excitement at the time with Walls quoting, generally without attribution, the numerous (and admittedly exaggerated) popular claims made about the work (statements made such as “scientists since Newton have been completely fooled about the way that the eye sees color”). After setting the stage with an entire column of these claims, Walls finally notes that Land has disavowed them! The remainder of the fourteen pages of the paper is replete with quotation marks essentially mocking Land’s work. In my view, even after this lengthy rant, he never provides an explanation for the experiments! In summary, this paper is certainly not objective science. So much for that!
I will not here attempt a complete characterization of Land’s work on color vision. Suffice it to say that his conclusions, drawn from measurements made external to the eye are, I believe, now explained by the geometric/optical antenna finding of my work. The parallels are dramatic – his observation that a wavelength dividing “fulcrum” must be present somewhere in the vision system is seen to correspond to the geometrically defined mid-band point at 7-8 degrees of retinal eccentricity that I geometrically define. Importantly, this fixed reference also explains for the first time the “color constancy” of vision. Land demonstrated, again from measurements made external to the eye, that the many hues of color are obtained by the eye calculating a ratio of light intensities (Land termed them “lightnesses”) on either side of this mid-band fulcrum point. This is the first place where the term color should be introduced in the vision process! Although Land deduced this without knowing the light interaction mechanism internal to the eye, my geometric explanation shows that the retina is sensitive to light intensities (his “lightnesses”) in three fixed- wavelength (RGB) bands and that these correspond to what have historically been termed the “primary colors”. One sees now, however, that these three wavelengths should not be termed “colors” at all reserving that term for the above defined ratio of light intensities on the retina.
In his work Land had available only the traditional model for light interaction in the eye. He proceeded, in the only way open to him, to develop an algorithmic theory – that he termed the “RETINEX” - to simulate the results of his color vision measurements. This work is a relatively difficult to follow and perhaps not necessary with this new corroborative understanding of the retina and the eye.
I have suggested that anyone interested in Land’s work should request the complete compendium of his papers from the Rowland Institute in Cambridge, MA that Land founded (that has now been subsumed into Harvard). These papers were sent to me in the early 1990’s by Holly Perry then in residence and who had been an associate of Land. She may have retired by by now but she was very helpful to me at the time. A review of these papers reveals the lucidity and true method of scientific inquiry characteristic of Land’s work. One must see the true character of scientific pursuit in this work! I have seen this only once before and that was in the writings of the physicist David Bohm!
One might also read Victor McElheny’s book “INSISTING ON THE IMPOSSIBLE - THE LIFE OF EDWIN LAND” (Perseus Books). Chapter 14 of the book describes in some popular detail Land’s color vision experiments. A quote (p.258) attributed to Land is particularly interesting here:
“Land spoke of the eye’s using light reflected from the scene to form at least two ‘identical but separate records of the scene’ one with longer wavelengths and the other with shorter” .
This is exactly where my explanation of light interaction with the retina leads. The dividing point between the two regions is the geometrically-determined wavelength reference at 7-8 degrees of retinal eccentricity (the exact center of midband G intensity that explains color constancy!) with Land’s long and short color vision records determined by ratioing intensities on either side.
It is my belief that Edwin Land was the true scientific genius of the field of color vision. His work should, and certainly will ultimately, be recognized!
Respectfully,
Gerald C. Huth, Ph.D.
Ojai, CA
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