Jim Worthey, Lighting and Color Research
home page contact about me
Jim Worthey • Lighting & Color Research • jim@jimworthey.com • 301-977-3551 • 11 Rye Court, Gaithersburg, MD 20878-1901, USA
Who is Jim Worthey?
I am an interdisciplinary scientist and engineer with
  • a BS in Electrical Engineering from University of Missouri, Columbia, Missouri.
  • an MS in Physics from Michigan State University, East Lansing, Michigan.
  • and a PhD in Physiological Optics from Indiana University, Bloomington, Indiana.

After receiving the MS in Physics, I worked a year as a teacher and then spent a few years as an engineer in a large factory. The factory work was fascinating because of the extent to which they made complex systems from simple materials. Raw chunks of steel and spools of wire were made into motors and generators and even into entire locomotives. The factory was also a sort of museum of bad lighting. Many of the big factory areas were lit with high pressure mercury vapor lights. These lamps present a small bright area, which is good, but they really lose colors. Mercury lights are used as examples in at least two of the articles linked from the home page: Color rendering, a new calculation that estimates colorimetric shifts, and the draft article Vectorial Color .

A stairway in one building had low pressure mercury vapor lights, something you will seldom see. These lights emit much of their light in the blue end of the spectrum, probably the 436 nm emission of mercury. Color contrasts are lost, which is bad, but there is also a special problem with blue light. The blue receptors in the eye are the least numerous, so vision with the blue receptors has a dreamy quality, lacking detail. Also, the mercury arc in these lamps would wander around the bulb, causing shadows to waver. I mention these experiences to explain how I got interested in lighting. I could see that lighting designs exerted strong control on a person's ability to see, but that the topic was not being discussed in clear terms.

It was with all this in mind that I went to graduate school a second time to study Physiological Optics. As a graduate degree program, Physiological Optics is the science of Human Vision as taught in colleges of Optometry. It is considered to be a broad interdisciplinary field, since vision involves optics and other physics, experimental psychology, physiology, and even genetics. I always kept my interest in physics and engineering. The term Physiological Optics arose in the 19th century when early research on human vision was done by physicists such as Hermann von Helmholtz.

People say that "you can never step in the same river twice," and that is certainly true of my experiences and education. Today at Indiana University and elsewhere, Physiological Optics is not taught in the same way---and there may be greater emphasis on things with a medical flavor. There may be more specific demands, such as a rule that Ph.D. students must work with an electron microscope, or work on research that has a sponsor.

In Color rendering, a new calculation that estimates colorimetric shifts, I give specific credit to one of my physics professors, Peter Signell. He was a tall, strong person who was able to write fast and clear on the blackboard, using a stout stick of chalk. Some of the important applied math came back to me from his lectures, not from any textbook. In the new work on vectorial color, I was guided by my early instruction on color vision from Professor Ronald W. Everson. Ron Everson taught the standard color vision material in a precise way that I clearly recall. We were left with an open question: "How is it that the chromaticity diagram identifies the possible mixtures of two given colors, presenting this information graphically and intuitively, but for the related question of how much of each light goes into the mixture, no graphical or intuitive method is given?" In 2003 and 2004, this question came back to me as I was studying a color space based on orthonormalized color matching functions. The spectrum locus in this space conveys the facts of color mixing with the amplitude information not left out. Ron Everson helped to frame this question, and when the answer was ready, it presented itself. Technical detail is on another page, monochromat.html.

Why is that web page called monochromat.html? In part, that involves another personal experience. In the color space of the orthonormal basis, Jozef Cohen called the spectrum locus "the locus of unit monochromats." By this he meant that if you could make a narrow-band light of wavelength lambda and unit power, then step lambda through the spectrum and plot the tristimulus vector of each narrow band, you would get this locus. Jozef preferred to use a different methodology and not the orthonormal basis, but the result is the same. Therefore Cohen's "locus of unit monochromats" is my "vectorial sensitivity to wavelength." It was my privilege to know Jozef Cohen personally, meeting him several times and discussing his work with him and with Michael Brill and others.

Note added 2004 November 4: As of today, the page with URL monochromat.html contains a new presentation entitled "Color Matching with Amplitude not Left Out." The topic is still vectorial color, responding to the question that arose in Ronald W. Everson's class in about 1974.

web site designed by
Nick Worthey
Copyright © 2002 - 2004 James A. Worthey, email: jim@jimworthey.com
Page last modified, 2006 June 17, 12:50 .