Saturday, 20 March 2010

Workshop: Color systems

By Dirk Metzmacher

You know RGB, CMYK and LAB, but only few designers know about the long history of very different systems that came before the ones we know today, a history that includes well-known names like Newton, da Vinci and Goethe, all of whom developed their own color theories.

Color theory

Everyone has heard terms like primary colors, subtractive or additive color mixing and color hexagon at some point. We encounter them every day, be it on a monitor or when using a printer. Let me just say CMYK and RGB.

1. The primary colors

The colors Red, Green and Blue correspond to the wavelengths of short wave, mid wave and long wave light and are often referred to as basic or primary colors. The combination of wavelengths in equal parts and full strength makes eight primary colors.

A primary color is one of the colors from which all other colors can be mixed, which are referred to as mixed colors or secondary colors. Color theory differentiates between additive and subtractive color mixing.
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Color systems

2. Subtractive color mixing

In subtractive color mixing, filters are used to filter the desired parts from white light, which contains all colors. These filters are color pigments that absorb certain bands of light. The most used filter colors are Cyan, Magenta and Yellow. These colors are also used in print, where they’re referred to as CMYK – the mixture of Cyan, Magenta, Yellow and Key (key color).

The key color K is usually Black and is not used for coloring, but for increasing contrast in dark areas. The term Key and the abbreviation K stands for Black or contrast and is used instead of Black, in order to avoid confusion with the B in Blue.

The print color Black is necessary, because printing the other three colors would only theoretically result in Black, but the colors used are not perfect.

3. Additive color mixing

In additive color mixing, lights are blended. The light of one color can have a color impression in different brightness values. With two primary colors you can create all colors in-between, which means in the color range on a straight line between those two colors. RGB stands for the colors Red, Green and Blue in full saturation.

4. The color hexagon

Here the colors Red, Green and Blue as well as Magenta, Yellow and Cyan are aligned in such a way that they create a double triangle, where the mixed values are arranged in-between. This way, there are always two colors directly opposite of each other that would result in White in additive color mixing or in Black in subtractive color mixing. Color counterparts like these are called complementary colors.

The color hexagon is divided into two halves. Cold hues are on the right side, warm hues on the left. Warm hues range from Green over Yellow and Red to Magenta. Cold hues range from Magenta over Blue and Cyan to Green. Magenta and Green are between warm and cold and are therefore considered neutral.

Color theory has a long history. Not only Leonardo da Vinci occupied himself with color, but also Newton and Goethe. A short summary of the history of chromatic circles will show you that the composition of colors is evolutionary, too.

1. Complementary colors

The colors that are opposite each other in the chromatic circle are called complementary colors. Due to their position they’re sometimes called opposing hues. They have a strong contrast and can create visual tension. The complementary color to Red is Turquoise, the one to Green is Purple and the one to Blue is Yellow.

People with color vision defects – such as a red green color deficiency – have trouble distinguishing between some complementary colors, because they have the same brightness value. Complementary colors are often used in advertising, because the color contrast attracts the viewer’s attention.

2. Short history of chromatic circles

Beginning with Leon Battista Alberti (1404-1472), over Newton (1643-1727) and Goethe (1749-1832) up to Itten (1888-1967) there have been many efforts in history to formulate an objectively justifiable ordering system for colors.

Leonardo da Vinci went by an arrangement of the four primary colors Yellow, Green, Blue and Red, such as his countryman Leon Battista Alberti created it in 1435. He realized that colors can not only be defined by their hue, but also by their brightness. The double cone according to Alberti puts the „uncolored“ colors at the tips of the cones.

The mixed colors are inside the double cone. Gray would be in the center of the middle section.

Isaac Newton constructs his chromatic circle according to the breakdown of daylight with the help of a prism. He observed seven colored elements which he arranged in a circle.

Goethe himself experimented with prisms, but he arranged his chromatic wheel differently. He believed that the colors originated in the human eye.

The chromatic wheel of Johannes Itten puts Yellow, Blue and Red together in a triangle. The successive triangles, which form a regular hexagon, display the secondary colors Green, Violet and Orange that result from subtractive color mixing. Itten defined a middle Yellow, a middle Red and a middle Blue as primary colors. Otherwise it would be impossible to mix every other color. Green is not a primary color for Itten.

The normed color space of the CIE is a current system and does not allow a mathematical determination of color differences. In the CIE Lab system, color differences are displayed as distances in a diagram.

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