HP PCL/PJL reference (PCL 5 Color) - Technical Reference Manual

A-10 Color Printing Overview (Color LaserJet, 5, 5M, DeskJet) EN
Device-Independent Color
The PCL language characterizes color as either device-dependent or
device-independent. Both categories encompass many color spaces,
each with unique characteristics.
Device-Dependent Color
Device-dependent color is relative to the device's inherent
characteristics. For example, the colors produced by plotters are
relative to the color of the installed plotter pens. Pen color varies
considerably, especially as pens wear out, changing the color of the
output. Likewise, for monitor screens, the red, green, and blue screen
phosphors determine the colors produced. Fully saturated colors can
vary greatly between screens. For printers, the color produced on a
page depends on the printer’s subtractive inks or toner (cyan,
magenta, yellow, and black).
When using device-dependent color, devices receiving relative color
specifications for the same color frequently do not produce the same
color. For example, a monitor’s saturated red may be different than a
plotter’s. In short, the same color page may appear considerably
different on different devices.
The HP color printers provide device-dependent color specified using
either the Device RGB or CMY color spaces.
Device-Independent Color
In contrast with device-dependent color, device-independent color is
based on an absolute color standard—the tristimulus values of
human vision. The device, whether a printer or otherwise, is
calibrated to match an independent color specification. The color
specification is translated in such a way that the resultant color is
independent of the device. Examples of color spaces based on
absolute standards include Kodak Photo YCC, CIE L*a*b*, YUV, and
the proposed YCrCb. Each is a transform from tristimulus CIE XYZ
space.