BASIC COLOR THEORY FOR PHOTOGRAPHERS

Color forms the basis for some of our strongest visual impressions. It is inherent to the functioning of nature as well as man-made reality (both as physicality and concept). The interrelationship of colors allows, in part, the efficient performance of life on this planet.

Stop signs are red because red stands out best against greenery (if foliage were orange, stop signs would probably be blue) and in order to survive, chameleons change color to blend with their environment. Color not only functions physically, but also conveys ideas and feelings, although in this more abstract sociological sense, color is subject to more rapid evolution.

As visual artists, it is impossible not to deal somehow with color whether we are seeking it out or avoiding it. Even as exclusively black and white photographers we must understand how color creates black and white tonality, how filters work, how panchromatic film is sensitive to all color while ortho-chromatic film and printing paper are not sensitive to red. We must learn how to see in black and white.

There are three sets of primary colors:

1. The primitive primaries: black, white, red, blue, and yellow (which operate on an intellectual, psychological level)
2. The physical primaries: red, blue, and yellow (which operate simply as definition of 'object reality'
3. The light primaries: red, blue, and green (which are a basic element in all molecular function, and determine our perception and graphic reproduction of the first two sets of primaries).

These three sets can be, but are not necessarily, related. For example, if we see a green leaf, the color "green", in this case, helps us to recognize and define the leaf as an object. However, even if we didn't see the leaf in these ways, or didn't see it all, or perhaps we're color blind, nevertheless the leaf would still be 'green' because that is part of its function. "Green", no matter what it is semantically called, is a very definite set of characteristics within the functional spectrum of radiant energy.

Objects appear colored because we are able to perceive them in that way. However, it has been almost positively determined that no mammals in the evolutionary scale up to the primates possess color vision, although many lower animals including birds, fish, reptiles, and some insects see color very well; this means that your dog or cat cannot distinguish color except as tonality (like black and white photographers).

But objects are colored, especially organic objects, because it is an important function of their molecular structure to absorb and reflect certain wavelengths of light. The leaf is what we call green because it absorbs red and blue light for use in photosynthesis, and reflects green light because it is of no use to its life functions. The leaf appears green, and as a side effect, we have a whole natural aesthetic system built around useless cast-off light.

Similarly, when an artist uses green paint, he is actually employing a molecular structure which absorbs red and blue light and reflects green light in order to maintain it's particular molecular structure. Function is a most basic attribute of color. Color is essential in making things what they are, not just in determining what they look like or mean. As an extension to this, we might theorize that black is the most functional color because it indicates complete absorption of all wavelengths of light energy, and white is the least functional because it indicates total reflection of all wavelengths of radiant light energy.

Color as physical description operates on a very simple yet useful level in our world. It helps us to learn, to recognize, and to discriminate; we learn and remember objects by their color (e.g., apples, oranges), we recognize products, places, and special objects by their color (e.g., a friend's yellow Volkswagen), and we discriminate quality and value by color (e.g., the ripeness of fruit, the quality of precious gems).

Perhaps because of our dependence on color as physical description, the majority of people are less attracted to, less able and inclined to deal with black and white or monochromatic versions of reality. This is evidenced by the modern move toward "punchy" color, and the overwhelming popularity of amateur color photography and color television. Physical color is seductive.

Color as a psychological agent works in complex, subjective, and often contradictory ways. It becomes symbolically attached to intricate or broad concepts (patriotism, money, nature); it is used to represent and reinforce religious ceremonies and seasons, and other human rituals (marriage, death). Psychological color denotes gender (pink for girls, blue for boys), signifies station and rank in life (blue-collar workers), and even sometimes defines personality and personality changes (a colorful personality, a black mood, the blues). Color also works psychologically to convey ideas and information important to our functioning (traffic signals, blindmen's canes, fire hydrants).

Although it is impossible in practice to separate the objective existence of color as molecular function from our subjective perception of it as neuro-psychological phenomena, it seems important that we more seriously consider the functional aspects of color as highly significant stimuli for biological motivation. When a house plant starts turning brown, do we water and sun it in order to return it to a more visually pleasing state, or to keep it alive? When one considers the amount of 'beautiful', carcinogenic 'Red dye #2' we consume, it seems likely that we should pay more attention to color as function.

So far we have dealt with existent color within three modes:primitive (psychological), physical (descriptive), and functional (the interaction of radiant energy and matter). Much less clear is the way in which humans perceive color (by a combination of eyes and brain), and how this perception is imitated and utilized through color photographic systems.

In understanding color perception, it is first important to realize the material inherence of color; if everything were not already inherently different colors, we would perceive monochromatically regardless of illumination or individual eye differences. Secondly, illumination plays an important role in the colors we actually see. We usually think of things as being the color we perceive them under "white light". However, "white light" is entirely relative; sun light, flood light, street light, car head lights, etc. are all different wavelengths within the spectrum, and as such affect the colors of the things they illuminate differently.

Moreover, in order to see a color, that color must be present specifically by wavelength within the wavelength range of the illumination. This causes few large problems when the illumination is "white light" of some variety, as it contains most of the visible spectrum, and the "color balance" is only shifted slightly by the variance of the white light range.

However, when the illumination contains only one wavelength or a limited range of the spectrum, objects will not necessarily reflect their actual color, or any color at all. For example, if you illuminate a red apple against a black background with a blue light, the apple will absorb all the blue light and reflect none, thus appearing grey and colorless. A banana under a blue light (against a black ground) will also appear grey, yet under a red light it will appear red, under a green light it will be green, and only under a combination of both the red and green lights will it appear yellow.

In considering our perception of color, we must also grasp the interrelationship of existent colors. Each object reflects a certain color, and as that color is added to the overall illumination of a given situation, all other objects will be affected by it, as well as our perception of the overall scene and each specific object in it. In the case of the apple and banana together under white light (against a black ground), the apple will absorb the extra yellow light and maintain its red color, but the banana (whose reflectance characteristic is a combination of red and green light) will reflect the additional red and thus appear somewhat orange.

There are no problems when dealing with only the three light primaries (red, blue, green) reflecting in each other's presence, as each primary color in reflection indicates the absorption of all other colors. However, rarely is the reflection that pure, and when complementaries or lower colors are present, interaction is inevitable. This is not an illusion, and can be recorded with color photographic materials.

Finally, we arrive at the highly subjective area of human color perception. This is a complicated matter which rests in the matrix of our eyes, nervous system, and brain, and in the physical and mental conditioning we have received. Because our color-seeing mechanisms are all slightly different, it is impossible to concoct a universally applicable color theory based on perception. However, a general theory (though still often controversial) has been constructed over the past 400 years which seems to account for most perceptual color phenomena. A summary of the major points is given here; for more detailed information, check the sources mentioned.

• White light contains all the colors of the spectrum.
• Natural bodies have physical colors which serve to absorb certain colors within the white light spectrum and reflect others as monochromatic light.
• The color and intensity of reflection from natural bodies varies with the source of illumination.

  - Isaac Newton, Opticks, 1704

• Color is sensation; each color has a different frequency or wavelength within the white light spectrum which physically vibrates the eye's receptors.
• Any and all colors within the light spectrum can be made by a mixture of the three light primary colors:red, blue, and green, and equal amounts of these three light colors add up to produce white light.
• There are three color sensitive kinds of receptors within the eye which respond respectively to red, blue, and green, and all color perception is a mixture of signals from these three receptor systems.

  - Thomas Young, 1802, and further developed by Helmholtz, 1855

• There are two different systems of photo-receptors in the retina:rods and cones. The rods do not perceive color; that is, they cannot distinguish wave frequency. They are sensitive only to variations in the intensity of illumination, and are used primarily for night or low light-level vision (some night animals have almost entirely rod receptors).
• The cones, which 'perceive' colors, become inactive in lower illumination. That is why objects appear colorless in very dim light, although we can still see relatively clearly when our rods have become adapted. For this same reason, many black and white photographers wear sunglasses to deliberately lower the activity of the color receptors.

  - Max Schultze, 1866

• The cones contain three different photosensitive pigments:erythrolabe, chlorolabe, and cyanolabe. Each exists separately in a different type of cone and is responsible for the absorption of each of the respective light primaries. Color blindness is thus explained as a lack of one or more of the three cone pegments contained in the normal trichromat retina.

  - Dobelle and MacNichol, 1964; Rushton, 1965

• Although all the spectral hues and white can be produced by mixture of the three primary light colors, it is not possible to produce any color that can be seen, such as brown and the metallic colors (the "sensation" of brown can be produced artificially by adapting the eye to blue and then stimulating it with intense yellow light).
• Certain colors such as brown require interpretation of areas of light rendered as object surfaces or photographic information before they can be uniquely perceived (yet in normal life, "brown" is one of the most common colors). Furthermore, objects such as apples or bananas become a richer and more natural color perceptual experience when the object is recognized. Thus, the brain makes invaluable additions to the eye's perceptions.

  - Edwin Land, 1964

Although there has been a great deal more fleshing out of these basic theories, this should provide a good basis for understanding the overview of color perception. At this point, it would be beneficial to discuss some perceptual color phenomena which can be useful in practice with either light or pigment.

First, we should distinguish between the light (additive) and the pigment (subtractive) systems of color. Additive color deals with the potential of different colors of light to 'add' up to white. Subtractive color deals with the potential of different pigments to 'subtract' from the reflectance of a ground toward black.

The additive primaries are red, green, and blue; the subtractive primaries are cyan, yellow, and magenta (or more primitively, blue, yellow and red). The result of mixing pairs of either set of primary colors are the complementary or secondary colors:

Additive Pairs	Complementary	Substractive Pairs	Complementary
Green & Blue	Cyan	Cyan & Yellow	Green
Red & Green	Yellow	Yellow & Magenta	Red
Blue & Red	Magenta	Magenta & Cyan	Blue

As you might notice, the additive complementaries are the same as the subtractive primaries, and the additive primaries are the same as the subtractive complementaries. This becomes very convenient in color photography and full-color reproduction, as we will find in the color separation process.

The complementary color for any specific primary is always the result of the mixture of the two remaining primary colors. For example, the complementary color to the additive primary blue is yellow (a mixture of red and green). To establish the relationships between primaries, complementaries, and other colors, it is usually helpful to set up a color wheel diagram. The complementary to any given primary is always its opposite on the color wheel:the color wheel works for both additive and subtractive systems by just reversing the values of the primaries and complementaries.

Joseph Albers spent a great deal of his life exploring the interaction of color in producing perceptual phenomena, the most notable of his work having to do with primary/complementary reactions, figure/ground relationships, and the relative position of colors in space. Some of his simplest findings can go a long way in practice:

• All colors give off or create a perceptual need for their complementaries as accidental color:e.g., a red object placed on a white surface and then removed will leave the "memory" of a faint cyan image. Furthermore, a color on a white surface or an abundance of a color in a composition creates a need for harmonious resolution by addition of its complementary. Single colors are unstable (thus, dynamic) in this way.
• Complementary colors (e.g., red and cyan) placed next to each other improve each other's brilliance/intensity by giving off each other as accidental color. Thus, the red appears redder, and the cyan appears more cyan.
• Grey receives the complementary hue of any color in its presence; e.g., grey placed next to yellow appears bluish-grey.
• In general, complementary colors produce the most "tasteful" relationships; they harmonize. Colors other than complementary which are brought together form less tasteful relationships and result in different perceptions of the original colors.
• Any prolonged or highly intensive viewing of a color stimulates the eye increasingly to produce the perceptual sensation of its complementaries, e.g., in looking at a dozen successive but identical samples of red, they will look successively more cyan. This is an important factor to consider when sequencing color material or imagery.
• In defining space through the relationships of colors, it is helpful to think of the colors in terms of superiority and inferiority. Colors work spatially according to temperature and luminosity with warmer, lighter colors being perceptually closer to the retina, and vice-versa.
• Color and color value inhabit and define natural space as degrees of chiaroscuro (alternating light and dark); the classical method calls for rendering of space to be carried out by means of complementaries harmoniously acting together in chiaroscuro.
• Of course, when non-rendered, unnatural space is desired, inharmonious, non-complementary colors are used and/or chiaroscuro is abandoned.