Konica Minolta Magicolor 7300 Reference Manual page 172

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
created on a device
like a monitor, using
the additive principle
and printing these
colors on a color
printer, using the
subtractive principle.
To print correct 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
translation 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.
164 Color Management