Konica Minolta magicolor 2350 Reference Manual page 170

Mixing equal amounts of cyan, magenta, and yellow pigments pro-
duces black pigment (because all the red, green, and blue portions of
white light are absorbed). Black, therefore, is the absence of color.
A color printer uses the subtractive principle, which means that when we look
at a color printout, the pigments in the toners absorb portions of the white light
reflected from the white substrate. A color laser printer typically ships with
four toner cartridges: cyan, magenta, yellow and black. Mixing equal amounts
of cyan, magenta, and yellow produces black. However, since color toners
are never 100% pure, black toner is added to provide pure black. Moreover,
black toner provides a more economical way to print in black only, such as for
text.
When we talk about
printing colors, we
actually talk about
matching a design cre-
ated on a device like a
monitor, using the
additive principle and
printing these colors
on a color printer,
using the subtractive
principle. To print cor-
rect colors we need a
module capable of
translating the RGB
colors of the monitor
into CMY(K) colors
used by color laser
printers. This translation is device dependent. The illustration shows such a
(software) module where certain RGB values (from a monitor) are converted
into CMYK values (for a color laser printer).
There are many devices capable of producing colors, like a monitor, a color
laser printer, a digital camera, and a scanner. To avoid a multitude of transla-
tion modules, we first need to define a standard for colors.
Since color is defined as how the human eye perceives this, we introduce the
CIE LAB color model (also called color space, the organization of all colors of
the visible spectrum in a device independent model). CIE is an acronym for
Commission Internationale d'Eclairage. Based on human perception, the CIE
LAB color model is most commonly used.
166—Chapter 4.1 Color Management