TEKTRONIX COLOR STANDARD


Overview:

The world of color is filled with ambiguous terminology, i.e.,
intensity, purity, value, etc. Many color users feel that "color theory"
is a prerequisite to operating color systems: TV, Videotaping,
Photography, Computer Graphics.

In order to end this confusion, Tektronix has developed a color language
and function based on human engineering, rather than machine engineering.
Below is a description of this system, which will providea clear and
concise means for understanding how color is defined and how our syntax
was derived.


Color Concepts:

Color selection is specified by Hue, Lightness and Saturation, which is
the HLS method.  The definitions are as follows:


Hue:         The characteristic associated with a color name
             such as red, yellow, green, blue, etc.  Hue is a 
             gradation of color advanced by degrees, thus
             represented as an angle from 0 to 360 degrees.

Lightness:   The characteristic that allows the color to be
             ranked on a scale from dark to light.  Lightness
             is expressed as a parameter ranging from 0 to 100%,
             with black being 0 percent (bottom of cone) and
             white being 100% (top of cone)

Saturation:  The characteristic which describes the extent to
             which a color differs from a gray of the same
             lightness.  Saturation is expressed as percentage,
             ranging from 0% (maximum white content at that
             lightness level) to 100% (full saturated).


Geometrically, colors can be described in terms of a "double cone",
two Euclidian cones joined at their bases.

Variations in lightness are represented along the axis, with white at
the apex of the cone and black at the opposite apex. Variations in
saturation are represented by radial distances from the lightness axis,
in constant lightness planes.  Hue is represented as an angular quantity
from a known reference point.