Color for Science, Art and Technology

Kurt Nassau, KURT NASSAU

• Publisher: North Holland
• Year: 1997
• Print ISBN: 9780444898463
• eBook ISBN: 9780080529370
• Topic: Ciencia de la computación
• Subtopic: Gráficos computacionales

The aim of this book is to assemble a series of chapters, written by experts in their fields, covering the basics of color - and then some more. In this way, readers are supplied with almost anything they want to know about color outside their own area of expertise. Thus, the color measurement expert, as well as the general reader, can find here information on the perception, causes, and uses of color. For the artist there are details on the causes, measurement, perception, and reproduction of color. Within each chapter, authors were requested to indicate directions of future efforts, where applicable. One might reasonably expect that all would have been learned about color in the more than three hundred years since Newton established the fundamentals of color science. This is not true because: • the measurement of color still has unresolved complexities (Chapter 2)• many of the fine details of color vision remain unknown (Chapter 3)• every few decades a new movement in art discovers original ways to use new pigments, and dyes continue to be discovered (Chapter 5)• the philosophical approach to color has not yet crystallized (Chapter 7)• new pigments and dyes continue to be discovered (Chapters 10 and 11)• the study of the biological and therapeutic effects of color is still in its infancy (Chapter 2).Color continues to develop towards maturity and the editor believes that there is much common ground between the sciences and the arts and that color is a major connecting bridge.

Section I

The Science of Color

chapter 1

Fundamentals of Color Science

Kurt Nassau Lebanon, NJ, USA (AT&TBell Telephone Laboratories Murray Hill, NJ, USA, retired)

1.1 Introduction

In this chapter we consider some basic concepts which are the essential underpinnings of all that follows. Some of these ideas are taught even as early as kindergarten, yet complexity is usually avoided at that level. Many may therefore continue to believe that there is just a single set of three primary colors, as one example. Again, it is often assumed that there is a unique color perception for each wavelength of the spectrum and that a given wavelength is perceived by everyone as the same color, whatever the circumstances, and that there is one unique, absolute white. So the aim here is to outline some color fundamentals and correct those misconceptions which may present difficulties in grasping more subtle advanced concepts later.

The reader should not be discouraged if some of this matter appears to be too abstruse or too naive. Merely skimming across such material should serve: this will acquaint the reader with its existence and will provide the setting for some of the items that follow. It is most desirable for such a reader to continue to the end, since the level in this, and indeed in all of the chapters of this book, varies considerably from section to section.

1.2 Defining color

Since color is a sensation unrelated to anything else, it is essentially impossible to give a meaningful definition except indirectly and circularly; for example: “Color is that aspect of perception which distinguishes red from green, etc.” A useful functional definition might be: “Color is that part of perception that is carried to us from our surroundings by differences in the wavelengths of light, is perceived by the eye, and is interpreted by the brain”. Again, we could say: “Our brain perceives color when a non-white distribution of light is received by the eye”. Yet it is easy to find flaws in and exceptions to any such definition. The painful tribulations of the Committee on Colorimetry of the Optical Society of America (Committee on Colorimetry 1953) to reach consensus on an adequate definition of color makes interesting but ultimately frustrating reading.

The term ‘color’ describes at least three subtly different aspects of reality. First, it denotes a property of an object, as in “green grass”. Second, it refers to a characteristic of light rays, as in “grass efficiently reflects green light (but see Section 1.4 below) while absorbing light of other colors more or less completely”. And, third, it specifies a class of sensations, as in “the brain’s interpretation of the eye’s detection of sunlight selectively reflected from grass results in the perception of green”. By careful wording one could always indicate which of these three (and other) types of meaning is intended in any given usage. In actual practice the distinction among such usages of color is not usually made, nor is any effort made here to do so. The mere awareness that such different aspects exist enables one to identify the intended meaning and save the use of many additional words. At the same time, it will be obvious to the discerning that some philosophical discussions on color are meaningless just because of confusion among such different aspects.

Sometimes such differences are, indeed, critical: ‘black’ (in the strictest sense) as used for the ‘color’ of a paint or the surface of an object has an exact meaning, namely zero transparency and zero reflectivity for all visually-perceived light. As the characteristic of a light ray, ‘black’ has no meaning at all. And in perception, the ideal ‘black’ is merely the total absence of visual sensation from a given region. These distinctions are also important to those who are involved with precise color communication (see Chapters 2 and 13 to 15), particularly when such communication places them in contact with others in different professions: these are circumstances where misunderstanding and confusion can so easily result.

1.3 Early views on color

The Greek philosopher, Plato, about 428–348 BC, held a pessimistic view on the possibility of a science of color:

“There will be no difficulty in seeing how and by what mixtures the colors are made … For God only has the knowledge and also the power which are able to combine many things into one and again resolve the one into many. But no man either is or ever will be able to accomplish either the one or the other operation” (MacAdam 1970, p. 1).

The view of the Greek philosopher Aristotle, 348–322 BC, dominated in the pre-experimental stage of science. Aristotle (or at least the writing attributed to him) noted that sunlight always becomes darkened or less intense in its interactions with objects and therefore viewed color as a mixture of white and black. To some of the Greeks it was the eye that sent out rays, acting like feelers, which detected the color of objects. Others believed that luminous objects emitted particles which were detected by the eye, while yet others believed that these objects emitted waves.

1.4 Newton, the spectrum, and “colored” light

The beginning of the science of color was described by Sir Isaac Newton, English mathematician and astronomer (1642–1727) in a report in the Philosophical Transactions for 1671:

“… in the beginning of the Year 1666 … I procured me a Triangular glass-Prisme … having darkened my chamber, and made a small hole in my window-shuts, to let in a convenient quantity of the Suns light, I placed my Prisme at its entrance, that it might...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Dedication
• Preface
• List of Contributors
• Biographical Notes
• Section I: The Science of Color
• Section II: Color in Art, Culture and Life
• Section III: Colorant, the Preservation and the Reproduction of Color
• Index