William Benson, c. late 19th centuryPart II: Ordering and Quantifying Color
The chemical makeup of colorants, dyes, and paints can be measured. Physically. the color of light can also be quantified by measuring the level of transmission. The color of an object can be quantified by measuring the level of reflectance. Colorimetry is the science of measuring color and uses mathematical ratios between phenomena to predict color accurately and uniformly. The eye cannot see the constituents of color, not intuit the operation of color. Colorimetric measurement can distinguish where perception cannot, for example, distinguishing between metamers (qualitatively differing lights that appear the same).
The Dimensions (or Attributes) of Color: Surface color is traditionally separated into three attributes, or dimensions: hue, value, and saturation. The attribute luminance is factored in (in place of value) when working with color in light. Hue refers to the quality commonly referred to simply as ‘color’. Value is the relative lightness of that hue, and saturation refers to its’ level of purity. A hue is the most saturated when it is closest to its’ purest state. A color becomes desaturated as it mixes with other colors or black or white. Two complementary colors will create a neutral, or gray when mixed in equal proportion. White, Black, and any mixture thereof is called achromatic, considered to be colorless because they are not a part of the visible spectrum. This seems curious since brown and chromatic gray cannot be seen in the spectrum but are considered chromatic because we know them to be composed of spectral colors. If the spectrum is made up of colors that combine to create all possible visible color, then must not black and white be a part of it?
Primary, Spectral, and Unique Colors: Spectral Colors are colors that can be seen on the visible spectrum at pure saturation. Unique colors are those that are strictly a single hue, and cannot be seen as part adjacent color on the spectrum. For instance, A unique red, is a red that is not bluish-red or yellowish-red. The definition of primary color is a difficult one, and one that may be confusing because there are different sets of accepted primary colors. One definition of primary color means that the color is irreducible: these colors cannot be created through an admixture. As Rainer Mausfeld points out in the Introduction to his book Colour Perception (Oxford University Press, 2003, p. 13), the “choice of the fiducial beams called the primaries is essentially arbitrary, except for the condition that no equation can be established”. Furthermore, The Blackwell Handbook of Perception (p. 96) reports “typically, three widely separated wavelengths are chosen as primaries and mixed to match the appearance of all other wavelengths. Because each investigator is free to choose the primaries, the empirical functions need not resemble each other but each data set presumably reflects the operation of the same three spectral filters in the visual system. Despite a century’s collection of precise three-primary color matches, it has been difficult to deduce a unique trio of spectral functions to describe the visual system’s fundamental filters. Indeed, if these fundamental filters are linear operators, there are an infinite number of filter trios that satisfy the data”.
Complementary Colors: These are perceptual opposites. These pairs of color will create a neutral gray when mixed additively.
Brown and Gray: What is brown, and what about gray? As mentioned above, though these colors don’t figure in many early and many simple color models, and they are not seen in the fully saturated spectrum, they are indeed variants of color. In the case of brown, it can be a variation of any color, a mixture of many different possible combinations. Gray can be separated into two types of gray: chromatic and achromatic. The former refers to grays that are the exact neutral point between complements, and the latter refers to a gray created by a mixture of black and white.
Tints and Shades: Though these terms are used colloquially to be a variation of a color, they have more precise meanings. A tint is a hue with white added, and a shade is a hue with black added.
Tone: This term is also often used to mean a variation, or modification of a color. Sometimes it more specifically refers to a hue modified with gray.
Contrast: The difference in visual properties that makes one color distinguishable from another. Color contrast can occur because of hue, value, or saturation difference, or a combination thereof.
Geometric and Symmetrical Color Models: Invented in 17th century Europe, color wheels, circles, and other models are organizational structures used to understand the potential “laws” of color operation. These are often used as a basis of reference and as a standard for color principles.
Mathematical/ Computational Color Space: The possible combinations of colors are infinite, and color models are inadequate at mapping color because of their finite nature and because the human eye does not see all colors equally. The first type of mathematical mapping of color perception was the 1931 CIE model, which took human perception (“normal observers”) into account. This method utilized what is called tristimulus values (roughly R, G, and B) to create a full color spectrum with these three primaries. Mapping color using tristimulus values creates what is known as a color space. There are 4 major models of color space (each has its own variations): CIE, RGB, CMYK, and HSL/HSV. They are outlined in the section below.
Some of the most influential historical color models and spaces and their descriptions are outlined here.
Isaac Newton: Principles of color have been understood within symmetrical circular-or other geometric shaped- diagrams since Issac Newton first placed what he believed were the seven colors of the spectrum into a circular shape. Though the spectral colors are now commonly divided into six-and most of us would be hard-pressed to see the color indigo in it-Newton believed in a correlation between music and art, sound and vision, and so developed a theory based on seven colors. Though this aspect of his discovery has been discredited, the notion lives on today in the popular memory-scheme ROYGBIV.
Johann Wolfgang von Goethe: Goethe wrote a treatise on color in 1810 called Zur Farbenlehre (The Theory of Colors). The book was basically an attack on Newton’s earlier Optiks. Goethe’s book was based on his own direct observation, and does not present a precise theory. His color circle was symmetrical and was the first to propose oppositional colors, anticipating Opponent-Process theory by more than 60 years.
Michel Eugene Chevereul: Chevereul was a French Chemist whose work as director of dye works in the tapestry industry led him to determine that perceived colors are altered by their adjacent color. His color circle-created for the dye industry-was created in the interest of maintaining uniformity in the field, had 72 increments. His book The Principles of Harmony and Contrast of Colors and their Application to the Arts had a great influence on French painters of the day.
Albert Munsell: 1905, three-dimensional color order system taking three features of color into account, designated as hue, chroma (saturation), and value (lightness).
Johannes Itten: Itten’s books and his 12-point star diagram are popular. If one reads his book carefully, there are instances of unusual and disturbing ideas on character as determined by complexion.
Josef Albers: Albers never developed a color model, but was and continues to be extremely influential. His experiments focused on the perceptual experience of color discovered through the simple act of looking. His work in painting and with his students centered around the relativity of color and simultaneous contrast.
CIE (CIE XYZ, CIE L*A*B*, CIE L*U*V*): (The International Commission on Illumination) As mentioned above the 1931 CIE XYZ model was the first mathematical color space, and is the basis for all other color spaces since. CIE L*U*V* modified the original to display color differences better. CIE L*A*B* was designed to be a more perceptually uniform (equal increments of change) space. CIEL*U*V* is used for additive mixtures, and CIEL*A*B* is commonly used for subtractive mixtures (surface colors).
RGB: Stands for red, green, blue. It has been known for over two hundred years, that these three colored lights can produce a full spectrum of colors. RGB is an additive color space the maps the gamut possible with these three colors. Projected color media like computer screens operate using RGB.
HSV/HSL: These acronyms stand for Hue, Saturation, and Value; and Hue, Saturation, Luminance respectively. These models are both based on the RGB model and are quite similar to each other. The difference between the two is that in HSL, Luminance replaces value.
CMYK: Stands for cyan, magenta, yellow, and black; the four colors of process printing inks. It is also a color space that maps the gamut possible with these four colors.
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