Examination

M any involved in the color reproduction process are learning about color the hard way, through trail and error – often at great expense.

The information in this book is intended to provide an understanding of basic color principles essential for making informed decisions during the color reproduction process.

It is important to know what color is a visual sensation that involves three elements – a light source, an object and a viewer. Without light, color would not exist. Light that appears white to us, such as light from the sun, is actually composed of many colors. If visible light is divided into thirds, the predominant colors are red, green and blue, which are the primary colors of light.
There are only two ways of reproducing color – additive and subtractive. Additive color involves the use of colored lights. It starts with darkness and mixes red, green and blue light together to produced other colors. When combined in equal amounts, the additive primary colors produce the appearance of white. Subtractive color involves colorants and reflected light. It uses cyan, magenta and yellow pigments or dyes to subtract portions of white light illuminating an object to produce other colors. When combined in equal amounts, pure subtractive primary colors produce the appearance of black.
It is the subtractive process that allows everyday objects around us to show color. For example, a red apple really has no color. Colorants in the apple's skin absorb the green and blue wavelengths of white light and reflect the red wavelengths back to the viewer, which evokes the sensation of red. All color printing processes use the subtractive process to reproduce color. Printing presses use transparent color inks that act as filters and subtract portions of the white light striking the image on paper to produce other colors.

To illustrate this, imagine three spotlights, one red, one green and one blue focused from the back of an ice arena on skates in an ice show. Where the blue and green spotlights overlap, the color cyan is produced; where the blue and red spotlights overlap, the color magenta is produced; where the red and green spotlights overlap the color yellow is produced. When added together, red, green and blue lights produce what we perceive as white light.

Television screens and computer monitors are examples of systems that use additive color. A mosaic of thousands of red, green and blue phosphor dots make up the images on video monitors. The phosphor dots emit light when activated electronically. It is the combination of different intensities of red, green and blue light that produces all the colors on a video monitor. Because the dots are so small and close together, we do not see them individually, but see the colors formed by the mixture of light. Colors often vary from one monitor to another. This is not now information to anyone who has visited an electronics store with various brands of televisions on display. Also, colors on monitors change over time. Currently, there are no colors standards for the phosphors used in manufacturing monitors for the graphics arts industry.

to summarize: Additive color involves the use of colored lights. It starts with darkness and mixes red, green and blue light together to produce other colors. When combined in equal amounts, the additive primary colors produce the appearance of white.