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Timeline of Mechanics, Electricity, Color and Lighting

Note: Most of the framework and details for events prior to year 1900 are from Wikipedia, except where it is obvious that original sources are cited. The goal is certainly not to rewrite history, but to call attention to the way that ideas evolve. Click here in order to skip ahead to the Detailed Chronology, which is the basis for the graphical timeline above. It includes many citations and links, including links to primary sources that are on the web. You can also skip to the bottom, the most recent items.

Newton:  In the late 1600s, Isaac Newton started a scientific revolution, for example by a new cause-and-effect understanding of planetary motion. Newton worked out his mechanics in one leap, and it is difficult to imagine it being otherwise. His laws of motion assume that friction is extraneous: "...a body in motion tends to remain in motion..." Very well, that almost makes sense, but he needed to take the next step and say "if I suppose frictionless motion and F=ma, what does that explain?" And then "suppose that planets move without friction." And then, "well, what keeps them on track? How about gravity?" To complete the picture, he wrote an algebraic law for gravity. Then, by the way, F=ma looks simple, but a is the second derivative of displacement with respect to time, so he had to invent calculus. He had to make a revolution. He couldn't make one timid advance at a time, really. He had to put all of his bold ideas on the table.

Let us now be bold and try to describe Newton's approach:
  • Seek simple laws.
  • Be bold. Don't cling to old assumptions.
  • Embrace math.
  • Don't ignore simple examples. The story of Newton and the apple tree is probably true, but in any event it has logic. The apple always falls toward the center of the earth. Perhaps the earth's pull reaches the moon!
  • Calculate some answers.
  • Let your concepts grow out of the simple laws and mathematics. Give precise meanings to words.

Another view is this. The time was ripe for Newton's ideas, but suppose that he had not appeared and a group of lesser minds had made his discoveries. They would still be geniuses, but maybe two mathematicians and two astronomers, reading each other's work. They would have had an extended period of uncertainty and controversy while they shared their ideas. They would have needed an atmosphere of patience and tolerance for uncertainty. Today, some scientists enjoy such a climate, but others do not

Big bang of engineering: The two centuries after Newton were a time of great progress for science in general and physics in particular. Engineering was systematic, but technologies were narrow. The 1800s were the age of steam. Also in that era, a funny thing happened. Great minds seemed to work harder and harder, and new ideas were formulated in detail by Gauss, Ohm, Faraday, Henry, Helmholtz, Hamilton, Boltzmann, Gibbs, and others. Using physics that was freshly made clear, Charles Proteus Steinmetz developed the concepts and wrote the textbooks of systematic electrical engineering. Then at the turn of the century, it was enough. You could call it the big bang of engineering, or maybe the ragtime singularity. Edison's electric lights (first patented in 1880) gave impetus and electrical engineers were ready to string their wires and electrify the world. With great new textbooks (plus slide rules and graph paper) engineers had the confidence to change the world. With their collection of ideas from the Ragtime Era, engineers could feel well-trained and even arrogant for a good 50 years. Even vacuum-tube amplifiers were mainly an application of 19th century physics. In the 1950s, transistors were a new paradigm but somebody had to wire them up, so traditional engineering remained vital.

While 19th century ideas were a legacy for engineers to study and apply,  physicists in the ragtime era were moving on. 1905 was Albert Einstein's Annus Mirabilis, in which he published 4 groundbreaking articles on the photoelectric effect, Brownian motion, special relativity, and mass-energy equivalence. That was the starting bell for a new era in which physics moved beyond the great discoveries of the 19th century.

So?? So engineers had what they needed, neatly packaged. That was all very well. They took their legacy for granted, as people do. But if we stop to think about the legacy, we notice:
  • A simple idea in freshman physics is that momentum, mv, is conserved. So is kinetic energy, (1/2)mv2 . But that's not really simple, it's confusing that the two derived quantities are both conserved. It took 100 years of discussion to sort it out. See the "vis viva" item below, a 2006 history of science article. So, there was a 100-year age of vis viva, or momentum and kinetic energy.
  • From Galvani's twitching frog legs to Maxwell's equations and Edison's first light bulb patent in 1880 was roughly a 100-year age of electricity.
  • From Galileo to William Rowan Hamilton is roughly a 200-year age of mechanics. Add on a few decades for Heaviside and Gibbs to develop vector methods as they now appear in textbooks.
  • From Newton to Maxwell and Helmholtz, count a 200-year age of color, from Newton's demonstrations and theory to the mature theory that Frederic Ives soon applied as a basis for color photography.
  • In short, it takes extended discussion by great minds so that a topic emerges clear and simple and ready for the engineering textbooks.

Now look for a creative period that establishes the scientific understanding of lighting. It has barely started. The traditional attitude is mainly that light is good.

  • Genesis Ch. 1, ver 3: "And God said, Let there be light and there was light."
  • Genesis Ch. 1, ver 16: "And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also."

So, light is good, and there are different kinds of light. That is very well. Artists might begin to notice more, how lighting conditions vary and how light interacts with objects. To take us toward scientific understanding, we have little legacy from ancient times, or from Galileo or Newton, or even Maxwell. To begin to understand lighting, we require the whole package of classical physics, from Newton's insight that white light is (usually) a mixture of all colors, to the laws of optics, and the methods of radiometry and photometry, plus some modern understanding of topics like color mixture. Late innovations to enable calibrated optical measurements were Grayson's ruling engine for diffraction gratings, described in a 1917 publication, and work, including by Langley, on measurement of optical power. (See below.)

Steinmetz's summer cabin, now in a museum.

Interior of Charles Proteus Steinmetz's summer cabin, now preserved at the Henry Ford Museum and Greenfield Village, near Detroit, Michigan.

Daylight is variable, but on a sunny day it comprises the rays from the sun's disk plus light from the rest of the sky dome. The sun covers only about 10-5 of the sky dome. ["Lighting quality and light source size," Journal of the IES 19(2):142-148 (Summer 1990). Web version.] Before electric lighting, artificial lights were flames: campfires, candles, oil lamps and so forth. At right is an interior view of Charles P. Steinmetz's summer cabin, showing among other things a kerosene lamp. (The cabin is preserved in a museum. The photo was taken by Nicholas J. Worthey in 2004.)

Then in the age of flame lighting, what did Edison invent? An incandescent lamp, with a filament that was relatively bright and compact and had the color of a flame. With present knowledge we can confirm that the filament was an approximate blackbody radiator and indeed had a spectrum similar to that from a flame. Edison probably understood as much--took it for granted.

In short, incandescent lights were a small step away from the world of flames for lighting. In the year 1912, a person could be an illuminating engineer, but he had mainly one source to work with. The engineering had to do with
  • The size and number of incandescent bulbs,
  • and where to put them,
  • and how to wire them up,
  • plus the design of glass globes and lenses.
Those were challenges enough. Other sources included carbon arcs and gas mantles, also physically compact and approximating the blackbody spectrum.
Steinmetz's summer cabin, now in

What would a scientific discussion of lighting look like?
An engineered light source accepts power in electrical form (usually) and by some physical process causes some of that power to be radiated as visible light. That light is reflected by objects that in themselves are not light sources. In reflecting the light, objects reveal themselves because they have textures, colors and shapes. The properties of the light and those of the objects become tangled together, then if a person views the scene, his visual system will, if possible, separate out the object properties. The person sees the objects and that experience is simple to him. The process of vision not really simple, but it seems simple because evolution has done such a good job with vision.

The way that the object and light become entangled and then the eye untangles them, those topics have been studied under such headings as color constancy and shape from shading. In the 20th century, Edwin Land did demonstrations to show the light's effect, and developed a theory to describe how the eye might compensate. Land's demos led to nicely illustrated articles in Scientific American magazine, which show the interesting apparatus that he built.
  • Land, Edwin H., “Experiments in Color Vision” Scientific American (May 1959): 84-99.
  • Land, Edwin H., “The retinex theory of color vision,” Sci. Am. 237(6): 108-128 (1977).
  • Land, Edwin H., “The retinex,” Am. Sci. 52(2): 247-264 (1964).
  • McCann, John J., Suzanne P. McKee, and Thomas H. Taylor, “Quantitative studies in retinex theory: a comparison between theoretical predictions and observer responses to the ‘color mondrian’ experiments,” Vision Res. 16, 445-458 (1976). (Based on Land's ideas and apparatus, though he was not an author.)
  • James A. Worthey, "Color rendering: asking the question," Color Research and Application 28(6):403-412, December 2003. (This article looks to the McCann, McKee and Taylor article just cited for some insight about lighting.)
The lighting user presumably wants to see, so he needs the disentangling process to work. A scientific study of lighting might begin with this broad insight, then move along to see how lights differ and how that affects vision. On that basis, and going back to the early days of electric lighting, one 1912 article stands out. [Herbert E. Ives, "The relation between the color of the illuminant and the color of the illuminated object," Transactions of the Illuminating Engineering Society 7:62-72.(1912).] The article is discussed below, but Herbert Ives's key observation was “It is, for instance, easily possible to make a subjective white, as by a mixture of monochromatic yellow and blue light. A white surface under this would look as it does under ‘daylight’ but hardly a single other color would.” Above is Fig. 1a from that article. The black lines are Ives's original drawing, then the orange and blue lines are added to represent his "mixture of monochromatic yellow and blue light".

The one 1912 article is discussed below and in the summary for the OSA 2014 Imaging Science meeting. It stands out as an early attempt to make a scientific cause-and-effect statement about one issue in lighting. Here are some reasons that Herbert Ives's remark is important:
  1. It hinges on a simple idea, but one that the reader may not have thought about. Even Newton, in his color article cited below, said that "whiteness ... [is] ever compounded, and to its composition are requisite all the aforesaid primary colours, mixed in a due proportion." Ives's reader in 1912, or 2014, might make a similar assumption. But Ives understood, perhaps from his own experiments, or from reading Maxwell, how vision really works. You can make a light as simple as "a mixture of monochromatic yellow and blue light" and it can be a visual match to white.
  2. In basic science and engineering, simple examples are a mainstay of teaching or discussion: a beam with no mass, frictionless motion, and so forth. But the two-bands light is a rare extreme case in the context of lighting.
  3. The example is described in physical terms, not in commercial jargon.
  4. Also, the example was essentially hypothetical in 1912. It did not refer to any perceived problem in the lighting business at that time. But in a scientific sense it was very real, based on the known functionality of human vision and a light that is physically possible.
  5. While the two-bands light was not a commercial product in 1912, it can help us to understand later commercial lights such as fluorescent, high-pressure mercury vapor and high-pressure sodium vapor.
  6. Suppose that one understands the two-bands light, and one has a favorite broad-band light such as daylight. Call them the bad light and the good light. Then it is easy to envision a mixture of the bad light and the good one, set to some standard of mediocrity. That is an approximate description of the spectra of fluorescent lamps, which combine blue light plus a broad band in the yellow.

In short, a scientific discussion should be thought-provoking, should build on prior knowledge, and should reveal a basic issue. Herbert Ives's remark answers that description. It appeared in Transactions of the Illuminating Engineering Society, Vol. 7. See below for more discussion.

The true illumination engineering lies in the steps that go beyond electricity and wiring: positioning the lamps and designing lenses, reflectors and the sources themselves. Electricity can power not only carbon arcs and filaments, but other lights which do not mimic flames at all. Before vapor discharge lamps were common, it was understood how strange they could be. US Patent 1025932, granted to C. P. Steinmetz in 1912 explains: "Hence it appears that an arc between electrodes, at least one. of which is formed of mercury, should be an extremely efficient light-giving arrangement, and this is indeed the fact, but the mercury arc is, unfortunately, of an extremely disagreeable color., It gives a discontinuous spectrum containing the Fraunhoefer lines 4047; 4359; 5461; 5769 and 5790, and some fainter intermediate lines. The sodium line, 5890, sometimes appears faintly, but this is probably due to the action of the glass or the presence of some impurity."

A scientific approach would give some thought to idiosyncratic lights, even hypothetical ones, and how they might affect vision of objects. Herbert Ives's passing remark in a 1912 article, discussed at right, calls our attention to a uniquely strange hypothetical light, a white light that comprises just two narrow bands, a blue and a yellow.

Ives's example was hypothetical but not impossible and its strangeness is echoed in 20th century technologies such as high-pressure mercury vapor lights, and even everyday fluorescent lights.

What does not live on is Ives's spirit of inquiry. His example, a kind of ideally bad light, does not speak to the physics of plasma discharges, but to the way the eye has evolved, with highly overlapping sensitivities in the red and green receptors. By the logic of the two-bands example, our vision of red-green object contrasts is uniquely at risk. But discussions of lighting and color seldom deal with these facts.

The two-band light is an extreme example for lighting and color. For the issue of light source size and placement, an extreme example would be that an object is lighted from all sides, as when it is in an integrating sphere. The discussion can then easily move to examples of compact sources (with small area) and the range in between. Other issues would call for other extreme examples.

A scientific approach would explore the cause-and-effect meaning of each issue and its extreme possibilities. In the 20th century, there was a problem that hypothetical sources remained hypothetical. It was not possible, on a reasonable budget, to build an apparatus that allowed an experimenter to manipulate a parameter such as light source spectrum in a systematic way. The exception that proved the rule was Edwin Land's experiments with projectors, cited at right.  The experiments stood out in that the experimenter could turn knobs and adjust the lights. It appears that the setups used considerable lab space and some money, but for a lighting experiment (rather than the interesting experiment that was done), even more projectors might be needed. (For readers who are not native speakers of English: "the exception that proves the rule" is an old expression meaning an exception or extreme case that tests a rule.) In principle, Land showed the way to new lighting experiments, but the apparatus was cumbersome and nobody extended his method to other kinds of experiments.

To learn more about the experiments with projectors as light sources, see http://mccannimaging.com/Retinex/Home.html , then visit the topics Color, Retinex, and Color Constancy .

21st century technology, especially LEDs, will give new possibilities for systematic experiments. It will still take some money and electronics skills.

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Detailed Chronology

Since 500 million years ago. Evolution of creatures with 2 eyes, including our mammalian ancestors:

The Visual
                  System: 500 Million Years of Evolution
Illustration developed by Nicholas Worthey. Chimpanzee photo by Thomas Lerch.

Galileo Galilei
Johannes Kepler

René Descartes

Christiaan Huygens

Christopher Wren

Isaac Newton 1642–1727
  • A Letter of Mr. Isaac Newton, Professor of the Mathematicks in the University of Cambridge; Containing His New Theory about Light and Colors: Sent by the Author to the Publisher from Cambridge, Febr. 6. 1671/72; In Order to be Communicated to the R. Society. Isaac Newton, Phil. Trans. 1671 6, 3075-3087  ,  doi: 10.1098/rstl.1671.0072  (Available from Jim W. or by searching on the doi. Wikimedia version.)
  • Principia Mathematica - 1687
Gottfried Wilhelm von Leibniz

Joseph-Louis Lagrange
"Lagrange was one of the creators of the calculus of variations, deriving the Euler–Lagrange equations for extrema of functionals. He also extended the method to take into account possible constraints, arriving at the method of Lagrange multipliers. ... In calculus, Lagrange developed a novel approach to interpolation and Taylor series. He studied the three-body problem for the Earth, Sun and Moon (1764) and the movement of Jupiter’s satellites (1766), and in 1772 found the special-case solutions to this problem that yield what are now known as Lagrangian points. " [Wikipedia, article on Lagrange.]
Luigi Galvani 1737–1798
Did famous experiments in which electricity caused a dead frog's leg to twitch, 1780. In one experiment, the frog's leg was in contact with dissimilar metals, which sufficed to make it twitch. That experiment was subject to interpretation, but led to the invention of batteries and the concept of a steady electric current as opposed to static electricity. By shocking body parts into action, Galvani inspired the fictional Dr. Frankenstein.
Alessandro Volta
Starting from Galvani's observations, Volta realized that when it was contacted by an arc of two dissimilar metals, the frog's leg was serving two purposes. It was in effect the electrolyte of a battery and also the detector of electricity. Volta then experimented with salt water as the electrolyte, and with various metals, developing primary batteries and the electrochemical series, 1800. [Wikipedia article on Volta.]

On 2015 Feb 18, Google published this animation to celebrate Volta's 270th birthday:
Animated gif,
                  Alessandro Volta's 270th birthday
Pierre-Simon Laplace
Introduction to Wikipedia article on Pierre-Simon Laplace:
"Pierre-Simon, marquis de Laplace (/ləˈplɑːs/; French: [pjɛʁ simɔ̃ laplas]; 23 March 1749 – 5 March 1827) was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five-volume Mécanique Céleste (Celestial Mechanics) (1799–1825). This work translated the geometric study of classical mechanics to one based on calculus, opening up a broader range of problems. In statistics, the Bayesian interpretation of probability was developed mainly by Laplace.[2]
Laplace formulated Laplace's equation, and pioneered the Laplace transform which appears in many branches of mathematical physics, a field that he took a leading role in forming. The Laplacian differential operator, widely used in mathematics, is also named after him. He restated and developed the nebular hypothesis of the origin of the solar system and was one of the first scientists to postulate the existence of black holes and the notion of gravitational collapse."
Carl Friedrich Gauss
Gauss is best known as a mathematician, but wrote "Gauss's Law," a fundamental equation in electricity that become one of Maxwell's equations.
Georg Simon Ohm 1789–1854 Published Ohm's law in Georg Simon Ohm, Die galvanische Kette, mathematisch bearbeitet, Berlin, Riemann, 245 pp., 1827 .   
Michael Faraday
One summary from Wikipedia: "His demonstrations established that a changing magnetic field produces an electric field; this relation was modelled mathematically by James Clerk Maxwell as Faraday's law, which subsequently became one of the four Maxwell equations, and which have in turn evolved into the generalization known today as field theory. Faraday would later use the principles he had discovered to construct the electric dynamo, the ancestor of modern power generators and the electric motor.
In 1839, he completed a series of experiments aimed at investigating the fundamental nature of electricity;
Joseph Henry
"He also discovered mutual inductance independently of Michael Faraday, (1791-1867), though Faraday was the first to publish his results." [Wikipedia, article on Joseph Henry.]
William Rowan Hamilton
Hamilton is remembered in particular for the Hamiltonian approach to mechanics. The Hamiltonian formulation can be applied to more complicated systems, when direct application of F=ma is not helpful. He invented quaternions. Modern vector methods are an alternative for many applications, but quaternions are still used, particularly to calculate rotations. 
Hermann von Helmholtz
"In physiology and psychology, he is known for his mathematics of the eye, theories of vision, ideas on the visual perception of space, color vision research, and on the sensation of tone, perception of sound, and empiricism. In physics, he is known for his theories on the conservation of energy, work in electrodynamics, chemical thermodynamics, and on a mechanical foundation of thermodynamics." [Wikipedia, Introduction to article on Helmholtz.]
On the science of the eye and vision, "
His main publication, entitled Handbuch der Physiologischen Optik (Handbook of Physiological Optics or Treatise on Physiological Optics), provided empirical theories on depth perception, color vision, and motion perception, and became the fundamental reference work in his field during the second half of the nineteenth century." [Wikipedia, article on Helmholtz, section entitled 'Ophthalmic optics.']
James Clerk Maxwell
  • James Clerk Maxwell, “Experiments on Colour, as Perceived by the Eye, with
    Remarks on Colour Blindness,” Transactions of the Royal Society of Edinburgh, Vol. XXI, Part II, 275-298 (1855). http://www.jimworthey.com/archive/index.html
  • James Clerk Maxwell, A Treatise on Electricity and Magnetism, Oxford: Clarendon Press, 1873. (2 volumes.)

Notice that even Maxwell's mathematical formulation of electricity and magnetism can be construed as an elaboration of earlier work by Faraday and others. The modern presentation of Maxwell's Equations as a set of 4 formulas in alternate forms is itself an extension of Maxwell's original treatise.

Ewald Hering
Hering is famous for his opponent-color theory of color vision, which he proposed in 1892. [Wikipedia, introduction to article on Ewald Hering].
Many sources (such as Wikipedia) may emphasize the dispute between Hering's opponent color theory and that of Thomas Young, James Clerk Maxwell, and Hermann von Helmholtz, who emphasized 3 primary colors, red, green and blue.  The Wikipedia article on Hering says "But nowadays we know that if the human possesses indeed 3 types of receptors as proposed by Young, Maxwell and Helmholtz they are then combined in 3 opponent channels as proposed by Hering. In their way both Hering and Helmholtz were right."

Wikipedia is correct that both Hering and Helmholtz were right. In this case, I (James Worthey) suggest that opponent colors is a bedrock idea that fits various kinds of evidence:
  • Intuitively, if you begin to name simple colors, you may easily notice an orange that is intermediate between yellow and red, or a yellow-green that is intermediate between yellow and green and so forth. But you will not observe a greenish red or a yellowish blue. It is intrinsic in the eye's function that blue and yellow are opposites, with white in the middle. Also red and green are opposites, with yellow or white in the middle.
  • Physiologists find red-green opponent cells within visual systems, and the processing from RGB to the opponent system takes place right in the retina. [David H. Hubel, Eye, brain, and vision, New York: Scientific American Library, 1968; paperback edition 1995. The book is now available on the web: http://hubel.med.harvard.edu/book/bcontex.htm .] [Webvision, The organization of the Retina and Visual System, edited by Helga Kolb, Eduardo Fernandez, and Ralph Nelson, Salt Lake City (UT): University of Utah Health Sciences Center; 1995-. Available on the web: http://www.ncbi.nlm.nih.gov/books/NBK11530/ ]
  • Sherman Lee Guth used opponent models to explain various results. [For example, Guth, Sherman Lee, Robert W. Massof, and Terry Benzschawel, “Vector model for normal and dichromatic color vision,” J. Opt. Soc. Am. 70, 197-212 (1980).] Also, there were experiments published beginning in the 1970s described as Minimally Distinct Border Experiments which are explained by opponent-colors.
  • The NTSC color television system from 1953 was based on an assumption about opponent processing in the eye, and also used an opponent principle in the way that color was encoded on the radio waves.
  • Since the overlapping red and green signals are correlated, it makes better use of bandwidth in the optic nerve to convert the cone signals to an opponent system. [Gershon Buchsbaum and A. Gottschalk, “Trichromacy, opponent colours coding and optimum colour information transmission in the retina,” Proc. R. Soc. Lond. B 220, 89-113 (1983).]
  • With a stated goal of understanding such ideas as Thornton's prime colors, plus some mathematical ideas, I derived an orthonormal opponent color system that is essentially the same result as that of Buchsbaum and Gottschalk, just cited. This system is then an aid to understanding and problem-solving. [James A. Worthey, "Vectorial color," Color Research and Application, 37(6):394-409 (December 2012).
    ] [Or, a preprint is at http://www.jimworthey.com/vectorial.pdf  ; be sure to download the figures: http://www.jimworthey.com/vectorialfigs.pdf ]

In short, then, we can give Hering credit and say that he discovered opponent colors in 1892, but the topic has been explored during the 20th century and into the present.
Samuel Pierpont Langley
Langley is famous for his aviation developments before the Wright brothers's first manned flight. He invented the bolometer, "an instrument for measuring infrared radiation," according to Wikipedia. His 1881 paper, The Bolometer and Radiant Energy, became a scientific classic. [Wikipedia article on Samuel Pierpont Langley.] Although I am frankly not finding more detail right now, I believe that Langley's work was pivotal in that he measured light by its heating effect, leading to related methods with "flat spectral response," as we would now say. Such objective measurements of radiation in the visible wavelength range were a prerequisite for measurements on humans leading to the 1924 Vλ function and the 1931 color-matching functions.
Josiah Willard Gibbs
Thermodynamics, Optics, Vector Calculus.
Thomas Alva Edison
Filed for his first electric light patent in 1879 and it was granted in 1880, U.S. patent 223,898 ,
Charles Proteus Steinmetz
Steinmetz was a mathematician and engineer. He held over 200 patents and studied lightning. But he also stands out as the man who literally wrote the book for 20th-century electrical engineers. Maxwell's equations are powerful but abstract. Ohm's law is simple, V=IR , but if V is time-varying, it does not apply to capacitors and inductors. Engineers often work with special cases in which V and I vary as sine waves. Steinmetz called on his mathematical training to simplify the algebra needed for such "AC circuits." He was a pivotal figure, establishing the terminology and methods so that electrical engineers can design systems and communicate with each other. Many of Steinmetz's writings can be found through archive.org and Google Books, including Theory and Calculation of Alternating Current Phenomena .

Looking at Steinmetz's contributions to AC circuit theory, we can say that the ideas were inevitable. For example, consider a capacitor (called a condenser in Steinmetz's day I believe) as an element in a circuit. Physics teaches that the current is proportional to the time derivative of voltage, I = C dV/dt . If applied voltage is a sinusoid, then you may write something like V = V0 sin(2πft) and I = 2πfCV0 cos(2πft) and so forth. The current is out of phase from the voltage. The current through a resistor is in phase with the voltage, and then if you add those currents you are adding a sine and a cosine with different amplitudes and some kind of trigonometric identity comes into play. An engineer would notice that he is doing much tedious algebra with great similarities from one problem to the next. Steinmetz realized that the repetitive steps could be written more easily and compactly using complex numbers. In effect, sine and cosine waves add as perpendicular vectors, while differentiation reduces to complex multiplication, and so forth. Because he worked quickly and wrote actual textbooks, his ideas must have gone in a short time from being unexpected and odd to being the iron-clad rules of self-confident engineers. History tends to celebrate tangible gadgets and not the books that the inventor read or wrote. However, it does appear that Steinmetz showed up at the right moment and was a smashing success as a textbook author, among his other accomplishments.

Steinmetz's writings covered DC and AC machines and more. I emphasize AC circuit theory to show how 20th century engineering came to be. By 1900, physics reached a plateau of completeness, a basis for design and analysis of practical machinery. Then a transition was needed, to take from physics a subset of ideas that can be applied again and again to analyze practical systems. In the electrical realm, Charles Proteus Steinmetz personified that transition and what it means to create a body of  practical methods based on valid science.

Henry Joseph Grayson
British-born Australian who made fine ruling engines for the production of diffraction gratings. While a prism can separate the colors of the spectrum, diffraction by a grating establishes wavelength in absolute distance units. Grayson developed a ruling engine for gratings. "In 1913 he was working full time on the grating project... . Grayson wrote an article on the engine in the Proceedings of the Royal Society of Victoria (1917) and was awarded the David Syme research prize in 1918." [Australian Dictionary of Biography, article on Grayson by H. C. Bolton]
Frederic Eugene Ives
Ives invented a method for full-color photographs that was "commercially available in England by late 1897 and in the US about a year later." [ Wikipedia article on F E Ives] The method was based explicitly on the trichromatic theory of color, as he explained:
  1. Ives, Frederic E., A new principle in heliochromy, Philadelphia: Printed by the author, 1889.
  2. Ives, Frederick E., “The optics of trichromatic photography,” Photographic Journal 40, 99-121 (1900).

These writings are available by searching on the web, or by contacting James Worthey.
In the book, item 1, Ives explains "This principle may be conveniently stated as that of producing sets of heliochromic negatives by the action of light rays in proportion as they affect the sets of nerve fibrils in the eye, and images or prints from such negatives with colors which represent the primary color sensations."

That statement, and the detailed explanation that goes along with it, lays out an idea that now can be called "The Maxwell-Ives Criterion." Today we see have the concepts of block diagrams and linear algebra, so a modern statement is Michael Brill's formulation:
Maxwell-Ives Criterion: The camera sensitivities should be linear transformations of those for the retinal cones.

Albert Einstein
In 1905, termed Einstein's Annus Mirabilis, he published 4 groundbreaking papers on
  • The photoelectric effect,
  • Brownian motion,
  • Special relativity, and
  • Mass-energy equivalence.
Herbert Eugene Ives
"Like his father Frederic Eugene Ives, Herbert was an expert on color photography. In 1924, he transmitted and reconstructed the first color facsimile, using color separations." He was president of the Optical Society of America in 1924-25. [ Wikipedia article on H E Ives ]  Of particular interest for this chronology of quantitative color is Herbert Ives's role in the development of the 1924 Luminosity Function, and an observation that he made about lighting and color. See the next item, concerning one volume of a journal about lighting.
Transactions of the Illuminating Engineering Society, Vol. 7.

Transactions of the IES, Volume 7, is available on Archive.org as one big file. Click the link above to download it. You will have 3 articles by Herbert E. Ives and other writings which reveal how lighting was understood, or not, 100+ years ago.
Transactions of the Illuminating Engineering Society, Volume 7, from the year 1912, contains 3 articles by Herbert E. Ives. Of particular interest are
  1. "The relation between the color of the illuminant and the color of the illuminated object," p. 62-72.
  2. "Heterochromatic photometry, and the primary standard of light," pp. 376-387.

The first article is on the topic that we might call "lighting and color," or "color rendering," although Ives's title is clear in itself. In that article he observed "It is, for instance, easily possible to make a subjective white, as by a mixture of monochromatic yellow and blue light. A white surface under this would look as it does under "daylight" but hardly a single other color would." Although Ives does not explain at length, he supplies a graph. We can assume that the monochromatic blue is at about 450 nm, and the yellow is at about 580.Sensitivities r g b as graphed by Herbert Ives See below, near the end of this timeline, how Thornton and Chen in 1978 revived Herbert Ives's 1912 idea of a white light that comprises a blue narrow band plus a yellow narrow band. Worthey drew the connection of the Thornton and Chen work to that of Ives. [James A. Worthey, "Limitations of color constancy," J. Opt. Soc. Am. A 2, 1014-1026 (1985). ]
Now, let us lay in the narrow bands that Ives described, "a mixture of monochromatic yellow and blue light."

This shows what Ives described but did not draw:

Herbert Ives drawing with the narrow bands
                      he described.

The two narrow bands are at 450 nm and 580 nm. The problem is, if you look at the graph, that the yellow light stimulates both the red-sensitive and the green-sensitive receptors. This two-bands light can be "daylight" color--a shade of white. Depending what shade of daylight you want to match, the amplitude and wavelength of the yellow band can be adjusted to refine the match. But the range of colored objects from red to yellow to green differ in how they reflect red, green and yellow light.

photo from Wikipedia, green-yellow-red peppers(Photo from Wikipedia.)

Red, yellow and green hues will not be distinguished if the light contains narrow-band yellow, but no red and no green. Herbert Ives was pointing out, in 1912, the issue that leads to "color rendering" problems, however you want to say it. And where did he publish this insight? In the Transactions of the Illuminating Engineering Society, the predecessor publication to the Journal of the IESNA, still put out by the same society. Of course the famous color-rendering document was first published by the CIE (Commission Internationale de L'Eclairage) in 1965. Did they acknowledge Ives's insight? No, not then and not now. Thornton and Chen called attention to the issue in 1978 (citation below). Worthey first used opponent colors as an approach to the same issue in 1982 (citation below). Opponent-colors thinking led to Vectorial Color. (Citations below.)

Vectorial Color is the answer to more than one problem, but look at the figure above, where narrow bands at 450 and 580 nanometers were laid into Ives's drawing. 580 is indeed yellow. Also in the drawing it is roughly the wavelength where the red and green sensitivities cross. That emphasizes that it stimulates both systems, so it "makes sense." But the point where those functions cross depends on the scale of the functions, so it's arbitrary. In his work under the heading of "Matrix R," Jozef Cohen revealed
a deeper truth about color mixing that does not depend on the way the sensitivities are scaled, or added and subtracted. Vectorial color combines Cohen's insights with the opponent-color formulation.

At left are the red, green, and blue receptor sensitivities based on the CIE 1931 observer. We can imagine a 2-bands light drawn in here, again at 450 and 580 nm.

2-bands light loses a dimension of color

At left is a self-explanatory figure based on the (xy) diagram and a 2-bands light slightly different from the one above.

Notice that lightmeter sensitivity, the y-bar function graphed below, is near its peak at yellow wavelengths of 570 to 580. So Ives's example is one that cheats on an illuminance requirement. It stimulates the lightmeter but deprives the user of red-green contrasts. Ives did not give a practical example, but fluorescent lamps (introduced about 1939) do this exact thing, presenting a 2-band spectrum, but with a broad yellow band so that red-green contrasts are not totally eliminated.

So that's color rendering. Traditional 4-foot or 8-foot fluorescent tubes have another failing. That is, the surface luminance is much lower than the luminance of a tungsten filament. The lower luminance source has a greater area, causing loss of shading, shadows and highlights, and converting the highlights to veiling reflections. Traditional fluorescent lights do everything wrong at once.

Transactions of the Illuminating Engineering Society, Vol. 7. 1912 In the same volume of Trans. Illum. Eng. Soc., the second Ives article deserves a separate discussion:
"Heterochromatic photometry, and the primary standard of light," pp. 376-387.

2-degree observer data published, along with the XYZ system for color algebra. 1931
The functions x-bar, y-bar, z-bar

Fluorescent lights introduced. Sources differ on the date, but they went commercial in about 1939.
Claude Elwood Shannon
Claude E. Shannon, "A Mathematical Theory of Communication," Bell System Technical Journal, Vol. 27, pp. 379–423, 623–656, 1948. Scans of the original articles are available:

However, an updated and reformatted version is linked at:  http://cm.bell-labs.com/cm/ms/what/shannonday/paper.html 

James Gleick's book The Information, cited below, puts information theory in context and explains its importance. Imaging, lighting, and vision itself are about the transmission of information. Contrasts are the stimulus to vision.   

The National Television System Committee was first established by the United States Federal Communications Commission in 1940 to establish a standard for analog black-and-white television. The committee was reconstituted in 1950 to standardize color television. [Wikipedia, article on NTSC.] As a standards committee, the NTSC was not necessarily a creative or scientific body. But the 1953 NTSC standard was based on analytical ideas about vision and color. It was a point of reference for applied color discussions and what works--what actually fools the eye. A textbook discussion of the fundamental color matching experiments may seem abstract and complicated. But every pixel of a TV picture is an example of additive color mixing. (Analog TV had bandwidth limitations, but not pixels as such.)
Hans E. J. Neugebauer

H. E. J. Neugebauer, “Quality Factor for Filters Whose Spectral Transmittances are Different from Color Mixture Curves, and Its Application to Color Photography,” J. Opt. Soc. Am. 46(10):821-824 (October 1956). Application of the Maxwell-Ives principle.
Michael J. Crowe

Michael J. Crowe, A History of Vector Analysis (Notre Dame, Indiana: University of Notre Dame Press, 1967); (New York: Dover, 1994). Vectors are a freshman topic and we take vector algebra for granted. But if you stop to think, the modern understanding is complicated:
  • Complex numbers add as 2-vectors, but have their own form of multiplication.
  • The inner product (dot product) is defined for 2-vectors, 3-vectors, or any dimension. But the result is a scalar, not a vector.
  • Cross product c = a×b gives a vector c perpendicular to the plane of a and b, so it is specifically a method for 3-space.
  • To write Maxwell's equations and other physics, we need those special symbols for vectorial partial derivatives. Those compact notations an innovation not available to Maxwell himself.
  • Rotation matrices work well for certain problems. To rotate objects in computer graphics, we need William Rowan Hamilton's quaternions.

Crowe's book reveals the struggles leading to this intricate schema. See a summary.

Jozef B. Cohen
  • Jozef B. Cohen, “Dependency of the spectral reflectance curves of the Munsell color chips,” Psychonom. Sci. 1, 369-370 (1964).
  • Cohen, Jozef and T. P. Friden, “Euclidean color space and its invariants,” Proceedings of the Technical Association of the Graphic Arts, 411-429 (1976).
  • Jozef B. Cohen and William E. Kappauf, “Metameric color stimuli, fundamental
    metamers, and Wyszecki’s metameric blacks,” Am. J. Psych. 95(4):537-564 (1982).
  • Jozef B. Cohen and William E. Kappauf, “Color mixture and fundamental metamers: Theory, algebra, geometry, application,” Am. J. Psych. 98(2):171-259, Summer 1985.
  • Jozef B. Cohen, Visual Color and Color Mixture: The Fundamental Color Space, University of Illinois Press, Champaign, Illinois, 2001, 248 pp.
William A. Thornton
  • William A. Thornton, “Luminosity and color-rendering capability of white light,” J. Opt. Soc. Am. 61(9):1155-1163 (September 1971).
  • Haft, H. H., and William A. Thornton, “High performance fluorescent lamps,”  J. Illum. Eng. Soc., 2(1):29-35, October 1972.
  • William A. Thornton, “Three-color visual response,” J. Opt. Soc. Am. 62(3):457-
    459 (1972).
  • Thornton, William A. and E. Chen, “What is visual clarity?” J. Illum. Eng. Soc. 7(2):85-94 (January 1978).
  • William A. Thornton, “A simple picture of matching lights,” J. Illum. Eng. Soc. 8(2):78-85 (1979).
  • Michael H. Brill, Graham D. Finlayson, Paul M. Hubel, William A. Thornton, “Prime Colors and Color Imaging,” Sixth Color Imaging Conference: Color Science, Systems and Applications, Nov. 17-20, 1998, Scottsdale, Arizona, USA. Publ. IS&T, Springfield, Virginia.

In the 4th item, “What is visual clarity?” Thornton and Chen revive Herbert Ives's suggestion (above) that a specified white can be matched by a mixture of 2 narrow bands. Their Fig. 1:
Thornton & Chen, 2-bands light


"ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks. The ATSC standards were developed in the early 1990s by the Grand Alliance, a consortium of electronics and telecommunications companies that assembled to develop a specification for what is now known as HDTV. ATSC formats also include standard-definition formats, although initially only HDTV services were launched in the digital format. " [Wikipedia article, http://en.wikipedia.org/wiki/Advanced_Television_Systems_Committee_standards ]

See the discussion above on the 1953 NTSC standard. The newer standards for high-definition TV are another reference point for thinking about analytical methods and what works for humans. Television standards are about delivering visual stimuli to users. "High Definition" implies high black-white and color contrasts (as appropriate to the original scene) with sharp edges.

Lighting systems control black-white and color contrasts that potentially exist in a scene. Lighting that pleases users will imbue a scene with the same virtues that are valued in high-definition video. In a way that is obvious and has been understood for decades. However
George E. Smith

George E. Smith, “The vis viva dispute: A controversy at the dawn of dynamics,” Physics Today, October 2006, pp. 31-36. In freshman physics, we learn that kinetic energy = E = ½mv2  and  momentum = p = mv. Both measures are conserved, but the conservation laws obviously differ in their details. Great minds struggled over which was the true measure of motion, mv or mv2  
  • “Near the end of 1668, ... John Wallis (1616–1703) and Christopher Wren (1632– 1723), submitted papers to the Royal Society presenting rules of impact.10
  • “Leibniz provoked the vis viva controversy in stages, beginning in 1686 and culminating in 1695.”
< The vis viva dispute is one topic in the pictorial timeline at the top of this page. >
James Worthey
"Opponent-colors approach to color rendering," J. Opt. Soc. Am. 72(1):74-82 (1982).

James A. Worthey, "Vectorial color," Color Research and Application, 37(6):394-409 (December 2012).

James A. Worthey, "Applications of vectorial color," Color Research and Application, 37(6):410-423 (December 2012).

Michael H. Brill

  • Michael Brill, Gerhard West, "Contributions to the theory of invariance of color under the condition of varying illumination," Journal of Mathematical Biology 11(3):337-350, March 1981.
  • Michael H. Brill, "Decomposition of Cohen's matrix R into simpler color invariants," American Journal of Psychology 98(4):625-634, Winter 1985.
  • Michael H. Brill and Henry Hemmendinger, "Illuminant dependence of object-color ordering," Die Farbe 32/33 (1985/6), 35-42.
  • Michael H. Brill, Letter to the Editor of  CR&A concerning a formal analogue to the spectrum locus based on the principal components in Cohen's 1964 article, Color Research and Application 12(4):226-227, August 1987.
  • Michael H. Brill, "Image segmentation by object color: a unifying framework and connection to color constancy," J. Opt. Soc. Am. A 7(10):2041-2047, 1990.
  • Hugh S. Fairman, Michael H. Brill, Henry Hemmendinger,"How the CIE 1931 Color-Matching Functions Were Derived from Wright–Guild Data," Color Research and Application 22(1):11-23, February 1997.
  • Michael H. Brill, Erratum to the article just cited, Color Research and Application 23(4):259, August 1998.
  • Michael H. Brill, "Color science applications of the Binet-Cauchy theorem," Color Research and Application 27(5):310-315, October 2002.
  • Hugh S. Fairman and Michael H. Brill, "The principal components of reflectances," Color Research and Application 29(2):104-110, April 2004.
  • Michael H. Brill and James Larimer, "Avoiding on-screen metamerism in N-primary displays," Journal of the Society for Information Display 13(6)509-516, June 2005.

Michael took responsibility for the final editing of Jozef B. Cohen's book, Visual Color and Color Mixture, published posthumously. See above.

James Gleick 1954- James Gleick, The Information: A History, a Theory, a Flood. New York: Pantheon Books, 2011.

Sean F Johnston, A History of Light and Colour Measurement, Bristol: Institute of Physics Publishing, 292 pages, 2001.
Johnston notes (at length) the peculiar beginnings of the profession of Illumination Engineering. The initial challenge was to quantify light. In the preface, p. ix: "
The measurement of brightness came to be invested with several purposes. It gained sporadic attention through the 18th century. Adopted alternately by astronomers and for the utilitarian needs of the gas lighting industry from the second half of the 19th century, it was appropriated by the nascent electric lighting industry to ‘prove’ the superiority of their technology. By the turn of the century the illuminating engineering movement was becoming an organized, if eclectic, community promoting research into the measurement of light intensity."

James K. Bowmaker
James K. Bowmaker, "Evolution of vertebrate visual pigments," Vision Research 48(20):2022-2014, September 2008. This review article is one reference for the pictorial on the evolution of the visual system, specifically the claim that trichromatic vision in simians evolved 35 million years ago. Many mammals have dichromatic vision, and a few are trichromatic, as Bowmaker explains in detail.

We found Bowmaker's interesting article free of charge: http://www.sciencedirect.com/science/article/pii/S004269890800148X  . Our search began with the powerful PubMed online index:  http://www.ncbi.nlm.nih.gov/pubmed  . PubMed indexes materials that are free and ones that are not free, but many interesting items are free.

There is a free textbook called Webvision that is hosted by National Library of Medicine and also by University of Utah:
http://www.ncbi.nlm.nih.gov/books/NBK11530/       or     http://webvision.med.utah.edu/   .
In Webvision, the emphasis is on anatomy, but some other topics are included.

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Copyright © 2014 James A. Worthey and Nicholas J. Worthey, email: jim@jimworthey.com
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