Konica Minolta AF-2840 Primary RGB and secondary CMY colors, Complementary colors, Green, Blue

AN INTRODUCTION TO COLOR

Primary (RGB) and secondary (CMY) colors

The RGB color model is an additive process that uses the primary colors of light: red, green, and blue. An additive color system mixes the three colors to recreate the entire spectrum of light. If all three colors are mixed, white light is produced. Television sets and computer monitors use RGB to create images.

The CMY color model is a subtractive process that uses the secondary colors: cyan, magenta, and yellow. A subtractive color system recreates color with pigments and dyes to absorb unwant- ed color. If all three colors are mixed, black is produced. Film-based photography is a subtractive process. Printing technology is also a subtractive process, but, unlike photographic systems, it requires a black channel (K). Because of the imperfections of printing inks, cyan, magenta, and yellow cannot produce a true black when mixed, printers use what is called a four-color process (CMYK) to reproduce images.

In photography, red, green, and blue are the primary colors. The secondary colors, cyan, magen- ta, and yellow, are made from combining the primary colors: cyan = blue + green, magenta = blue

+red, and yellow = red + green. The primary and secondary colors are grouped in complemen- tary pairs: red and cyan, green and magenta, and blue and yellow.

Complementary colors

Knowing the complementary colors is very important in color balancing. If the image has a specif- ic color cast, either subtracting the color or adding its complementary color will create a natural looking image.

RED	Decrease the amount of red.
GREEN	Decrease the amount of green.
BLUE	Decrease the amount of blue.
If the image is too…	Increase the amount of red.
CYAN
MAGENTA	Increase the amount of green.
YELLOW	Increase the amount of blue.

Adding or subtracting equal parts of red, green, and blue will have no effect on the color balance. However, it can change the overall image brightness and contrast. Usually, no more than two color channels are needed to color balance an image.

Color balancing is a skill that develops with practice. While the human eye is extremely sensitive in making comparative judgements, it is a poor tool when making absolute measurements of color. Initially, it can be very difficult to distinguish between blue and cyan, and red and magenta. However, adjusting the wrong color channel never improves an image; subtracting blue from an image that is too cyan will give a green cast to the image.

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