Proceedings of 2nd International Symposium for Color Science and Art 2020

Art, Reproduction Technology, and Science:
Foundations of Understanding ColorJohn McCannMcCann Imaging, Arlington, MA 02474, USAABSTRACT• Physics describes the interaction of light andmatter. Although discussed by the ancient Greeks,
Molecular Physics has advanced most rapidly inthe past three centuries.
• Color Vision research describes the mechanisms
used in seeing: optics of the eye; retinal cells that
respond to visible photons; nerve cell response,
spatial comparison of neural response; sensations,and perceptions of color.
This talk studies these four different threads of Color.
More important, it emphasizes how they weave together
to influence, and advance each other. To understandColor, one has to study all of its historical threads. Thelong history of Picture Making is the story of artists
painting and printing them. In 1800, photography andstudies of light/matter interactions started the Molecular
Physics technologies of film, digital sensors, and displaysof today.
Picture Making’s biggest challenge is rendering thereal-world’s High Dynamic Range (HDR) of light. Painters
met that challenge in 1500, and physics-based
technology is fighting with it today. This talk uses HDR
imaging as a test of Picture Making, and a signature ofhuman Color Vision’s mechanisms.

Understanding Color is the fusion of today’s imaging
technology with our 160-century history of making
pictures. Molecular physics describes the mechanisms oflight-matter interactions, while painters and picture
makers have led the way to understanding how we see
Color. The painter’s hand is controlled by his Color
Vision. While Molecular Physics happens at the atomic
scale, Color Vision is controlled by neurons interactingwith the entire scene. The threads of Painting,Reproduction Technology, Physics, and human Color
Vision weave together to make 2020‘s Color.
1. INTRODUCTION
Our understanding of Color is both practical andscientific. The practical part is the art of painting pictures,and the technology of reproducing scenes. The scientificpart is the interaction of light and matter. Physics
provides understanding of electromagnetic visible light(wavelengths between 400 and 700 nm). Somemolecules (colorants) modify the wavelength distributionof the illumination‘s light. Other atoms and molecules
emit light. All of color physics happens at a submicroscopic, molecular scale. More important, theselight /matter interactions at each location in the scene are
independent of all other parts of the scene. In otherwords, Molecular Physics describes local events.
Color in practical Picture Making is different. It uses
the viewer’s entire visual system as the most importantpart of the process, whether painting a landscape, ormaking firmware for a camera. The picture’s appearance
is the output of the viewer’s neural comparisons of all
scene elements. Appearance (sensations) depends on
the interaction of all of vision, and the entire scene. In
other words, human vision uses light from all parts of thescene to make the appearance of each scene element.
While local Molecular Physics events are necessary,vision also requires neural Spatial Comparisons madeacross the entire scene to make pictures. We know thisbecause two identical spots of light can appear different
colors in the same real-life scene.
Human fascination with Pictures Making goes back toman’s earliest recorded history.
• Painting requires the combination of tools andhuman vision to guide the artist’s hand in rendering
appearances.
• Printing goes back to rubbings of the earliest coins,and embossed clay. An artist’s hand made themaster, and technology made identical copies.

2. SNAPSHOTS IN TIME
Color becomes much more interesting when wecompare the threads at the same time in history. Whilepainting and printing made significant developments
centuries earlier, physics and color vision research haverecently caught up in importance for the future. The
following snapshot examples illustrates how these
historical threads interacted.
In 1500, at the height of the Italian Renaissance,
painting was revolutionized by the use of perspective andchiaroscuro (light and dark rendition). Perspective
imposed scientific rules controlling the size relationshipsof objects in the scene. Leonardo da Vinci invented
chiaroscuro to unify the rendition of light and shadows
throughout a painting. This began the rendition of HighDynamic Range (HDR) pictures. Also, Leonardo
observed that colors appear most beautiful whensurrounded by their opposites.
Around 1700 Newton’s physics experiments separated
white light’s different “refrangibilities” (wavelengths) thatappear red, yellow, green, blue and violet colors. He
used a second prism to recombine those wavelengths
into white light. Newton’s Color Vision observation was:4

Proceedings of 2nd International Symposium for Color Science and Art 2020
best elements of old and new into today’s photography.
The history of Color is the fusion of Art, Picture
Making, Physics and studies of Color Vision. Some of themost important contributors to understanding color madeextraordinary contributions to more than one of its fields:• Leonardo - Painting and Color Vision• Newton - Physics of light and Color Vision• Maxwell - Color Matching and Color Photography• Land - Instant Photography and Color Vision
These students of color amplified their contributions byworking in several fields. Newton’s double prism
experiment separated different wavelengths, and thenrecombined them. There, he identified light’s physicalproperties. When he described what these wavelenths
looked like, he knew that he was working in another field.
Newton separated the physics of light from light’s action
in human vision, describing it as “stir up a Sensation”.
Land was an expert in making silver halide and dyeimages. As soon as he saw the wide range of colors in
red and white (2-color) photographs, he knew that themechanisms controlling color appearance werefundamentally different from those controlling color infilms. He knew that RGB separations, used since LeBlon,
were made by local Molecular Physics interactions. Heknew the human retinal receptors used the same
physics-based mechanisms. Land recognized that
Molecular Physics is necessary, but not enough toexplain what we see. Additional mechanisms are needed
to understand Color Appearance and Color Constancy.
Land turned to Spatial Comparisons across scene.

“For the Rays to speak properly are not coloured. In them
there is nothing else than a certain Power andDisposition to stir up a Sensation of this or thatColour." [1] The double prism experiment, separated thephysics of light from the action of human vision, namely“stirring up a Sensation”. Also in 1700, Mezzotint printing
plates became popular for their efficiency. By using
different “rocker” tools to roughen metal plates, printersformed different tone textures, that transferred different
amounts of ink to the print paper. LeBlon used threecolor, plus a black mezzotint plates to become the color
printmaker for the French court. In Holland, Vermeer
painted “Girl with Pearl Earring” rendering the model andthe scene’s illumination in a remarkable HDR portrait.
In 1802, Thomas Young wrote “On the Theory of Lightand Colours” with a footnote suggesting that humanColor Vision was trichromatic. That footnote does not
explain his observation. Color-printing was everywhere inLondon at the time. LeBlon’s 1707 Mezzotints show an
example of theory following practice. in 1810, Goethe,
the German poet, began a psychological branch of Colorby attacking Newton’s work and Newton’s character.
Rather than repeating Newton’s experiments, Goethe
held a prism in front of his eye. He did not understandwhat he saw. Goethe’s reports about afterimages, andopponent colors emphasized human vision. Goethe
missed Newton’s statements about “stirring upSensations”. Nevertheless, he started two centuries ofdebate on the relative importance of light vs. vision.
Today, Molecular Physics has produced color pictureswith remarkable improvements in the control of spectral
light, with much better color purity and chroma. Color
Vision research has provided many more details andmeasurements of Spatial Comparisons with the study ofpsychophysics and neurophysiology.
3. FRAMEWORK FOR UNDERSTANDING COLOR
Aristotle segmented his writing into books, each withrelated studies. This tradition of segmentation continues
in Universities, with Departments, and Divisions, such as
Arts, Humanities, Science, and Engineering. But, Coloris an essential part of many studies. Color does notbelong to a single field: It is a fusion of all of its different
parts. It builds on the integration of the best elements ofcompeting systems.
A good example of fusion is the complete
transformation of Photography over the past 40 years. In1980, the photographic film industry made many millionsof cameras and billions of photographs. By 1990, many
companies made massive investments in digital
photography. In 2000, mature digital products began toreplace almost all film. The features of cost per picture,access to stored images, customer behavior, andespecially the ability of easy transport of images on theinternet morphed a very mature film industry into an
entirely different digital one. Digital photography fused theFig. 1 List of author’s foundational Ideas: Year, Idea,and Field of Study. (Historical references [2] )3.1 Personal Color Frameworks
Each of us has a personal Framework of Color. Fig.1
is the list of ideas that form the foundation of my thinking
about color. It is made up of ideas from many different
disciplines. In high school I loved Chemistry. In college I
traveled from Chemistry to Biochemistry to Biology, whileworking part-time for Edwin Land at Polaroid. My work at
Polaroid studied color vision, computer models of vision,,5

Proceedings of 2nd International Symposium for Color Science and Art 2020
Psychophysical measurements of the conversion oflight to appearance have observed different results fordifferent scenes. The appearances of spots of light leadto different models than real-world scenes. Spatial
Comparison mechanisms are needed in real scenes andcomplex scene constructions.

very-large format Polaroid cameras, and the reproductionof art. I set up Polaroid’s first digital imaging lab in 1975
to model human Spatial Comparisons.
Fig. 1 is a list of essential ideas in my own research. I
worked backwards from current interests to identify its
most important foundations. The list includes originaldate, author who reported it, and the idea’s Field. Whilethese ideas are special for me, the more interesting list is
the Fields they came from. It shows themes of interest inlight and molecular physics, as well as how to understandvision and computer models of it. However, many of myimportant ideas are not main-stream to my themes.
These ideas come from other Fields.
The first challenge in fusing different views is that eachdiscipline uses its own vocabulary. Too often the samewords have conflicting definitions. Contrast is a word
common to all parts of color. But, photographers think ofContrast as the “slope of response function”, whileelectrical engineers think of it as “black level setting”.
Painters, neurophysiologists, computer programmers add
their own special meanings. Patience is necessary towander into other Fields, particularly in learning themeaning of unfamiliar terminology.
Finding how to use the ideas from different Fields isrewarding. It can end needless debates, and generate
insight and understanding. Try making your own Color
Framework of the ideas that are most important to you.

4. CONCLUSIONS
Recent applications of Molecular Physics andengineering brought us today’s color pictures. Colorkeeps getting better at a faster and faster rate.
Nevertheless, understanding how we see Color remains
a fascinating topic with problems to be solved.
Understanding them needs our entire color history. While
we recognize the many recent advances in MolecularPhysics, we have a new appreciation of the role of neural
Spatial Comparisons. Color photography’s three
separations are the result of Molecular Physics. Color
Vision’s three separations are the result of neural Spatial
Comparisons. Light controls technology, but neurons
control color appearance. Light/matter interactions
happen in the space of molecules. Appearance involves
processing the entire scene, so that models of vision
demand data from all receptors. Both the mechanism,and the data required are important parts ofunderstanding Color.
Two experimental studies are important in evaluating
real-world vision: Color Constancy and HDR Color.
Constancy works best in low-range scenes made ofuniform reflectances. It has been measured and modeled
successfully using Spatial Comparisons. Further, Color
Constancy is inconsistent with retinal adaptation
mechanisms.[5] Measurements of Color Constancy in
HDR scenes have shown that edges in illumination(shadows and specular reflections) are seen the same asedges in reflectance. In HDR scenes Constancy is limited
to l ocal segments. N everthel ess, the S p at ial
Comparisons that compensate for glare combine with
Spatial Comparisons for Constancy to model real-world
color.

3.2 Story of Color
The Framework in Fig. 1 leads to my condensation ofresearch in color. The chain of events leads to seeing
Color in a real-life scene:• Light/matter interactions controls light reaching eye• Molecular Physics• Optical Glare controls the image on the retina• Glare Spread Function (GSF)• Receptors convert light to nerve response• Molecular Physics• Neural processing• Counteracts Glare [3]• Spatial Comparisons• Controls Color Constancy [4]• Spatial Comparisons

6. REFERENCES[1] I. Newton, “Opticks”, 4th ed. (1730); DoverPublications, Inc., New York, N.Y, p. 122, (1952).
[2] Historical Bibliography <https://mccannimaging.com/col_lab/Framework.html>[3] J. McCann & V. Vonikakis, “Calculating Retinal
Contrast from Scene Content: A Program”, Front.
Psychol., 17 Jan 2018 | https://doi.org/10.3389/fpsyg.
2017.02079[4] J. McCann, C. Parraman, A. Rizzi, ÒReßectance,
illumination, and appearance in color constancy”,
Front. Psychol., 24 Jan 2014 | https://doi.org/10.3389/fpsyg.2014.00005[5 ] J. McCann, “Limits of Color Constancy: Comparisonof the signatures of chromatic adaptation and spatialcomparisons”, In Proc. Electronic Imaging, IS&T, San
Francisco, (2019). <https://doi.org/10.2352/ISSN.
2470-1173.2019.14.COLOR-085 >The most common issue in understanding color resultsfrom applying the rules for Molecular Physics directly tothe prediction of color appearance. Leonardo observedthat Color Vision responds to the scene. This idea has
been reinforced by LeBlon, Goethe, Herring, Land, Hubel& Wiesel, Dowling, and Campbell. Molecular Physics
controls the light reaching the eye, and the response ofreceptor outer segments. But, it does not control
appearance. There is no light from the surround in
Maxwell’s Colorimetry. Hence no glare, and the only
Spatial Comparison is between the uniform spot to theminimal light surround.

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