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Tuesday, December 21, 2010

Color Theory Explained

Having a solid understanding of digital color theory will make you a better all-around photographer. Digital expert John Paul Caponigro explains the ins and outs.

This Article Features Photo Zoom

3) Bisecting a color wheel with a straight line defines complements, colors that produce a neutral color when mixed in equal proportions. Increasing one color reduces its complement. Three complementary axes are particularly important in color adjustment—red/cyan (0/180), yellow/blue (60/240) and green/magenta (120/300).
If Color Theory Is A Language, What Is Its Vocabulary?
The language of color theory can be confusing, due in part to a general lack of familiarity with its terms (it’s not as widely known as it should be) and in part to its varied terminology (its vocabulary hasn’t been decisively defined).

At its most basic, color consists of three elements—hue (red, orange, yellow, green, blue, purple), saturation (neutral, semi-neutral, semi-saturated, saturated, super-saturated) and luminosity (dark, light).

Many words can be used to describe the same elements, which leads to confusion. Color is often used to describe hue, which is only one aspect of color. Color is the combination of three elements—hue, saturation and luminosity. Brightness, also called luminosity, also called value, can be confused with saturation. Saturation, also called intensity, also called chroma that’s sometimes confused with hue, can be confused with how much colorant permeates a surface, which, though related, is a separate factor. If you’re confused now, that’s perfectly normal. A widespread adoption of a consistent set of words would go a long way toward making communication about color more precise, but it hasn’t happened yet. For the purpose of this article, I’ll default to the terms luminosity, hue and saturation as they’re useful terms in Photoshop (they describe blend modes and are nearly identical to the HSB readouts in Photoshop’s Info palette).

4) The line drawn between 90 and 270 degrees separates warm from cool colors; everything left of this line is cool; everything right of this line is warm. Warm and cool are psychological descriptors of color and are relative. Two colors can be considered absolutely warm (red) and cool (cyan). Any move toward red can be considered a warming adjustment. Any move toward cyan can be considered a cooling adjustment.
These three elements—hue, saturation and luminosity—can be represented numerically. Photoshop provides readouts in its Info palette in several color modes, including HSB (hue, saturation, brightness), found in the submenu beneath the arrow. Luminosity is represented on a scale of 1 to 100. (It’s a scale of 1 to 10 times 10. Put another way, it’s the photographic Zone system times 10.) Saturation is also represented on a scale of 1 to 100. Hue is represented on a scale of 0 to 360—the number of degrees in a circle or wheel.

This representation of color makes hue the only element of color for which the numerical language is conceptually challenging. Several things will make using this scale easier. You can think of the color wheel as a clock, where every hour (or 30 degrees) you get a new color. The wheel starts at a warm (yellow) red (0 degrees), 30 degrees is orange, 60 is yellow, 90 is warm (yellow) green, 120 is green, 150 is cool (blue) green, 180 is cool (green) blue or cyan, 210 is blue, 240 is warm (red) blue, 270 is purple, 300 is magenta and 330 is cool (blue) red. An image could be considered to be monochromatic if it uses hues constrained within 30 degrees or less from one another. Analogous hues are within 60 degrees of one another. Complementary hues are 180 degrees apart.

Linguistic descriptions of color are less precise than numeric descriptions of color. Consider forming consensus around terms such as sea foam or dusty rose. What color is mauve? More to the point, how many colors can the term mauve be used to describe?

5) Concentric circles can be imposed upon a color wheel to define the saturation level of a color or a set of colors—neutral, semi-neutral, semi-saturated, saturated or super-saturated. 6) Shapes can be imposed upon a color wheel to help identify a variety of ways to structure hues.

Using numbers to describe the elements of color leads to a more precise definition of color. Consider the usefulness of specification systems like Pantone. In numerical systems, there’s only one color for a single number or set of numbers. In addition to precision, one of the characteristics that makes a numerical system useful conceptually is its simplicity. Compare memorizing the numbers in the Pantone system with understanding the numerical scales in HSB. Not all systems are simple enough to be used conceptually; HSB is.


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