# Theatre Design & Technology - Oct 1972 - 23

```A UNIFORM NUMERICAL COLOR MEDIA
CODING SYSTEM
WILLIAM D. LITTLE
At the present time in the performing arts trades, the
use of color media is an accepted fact and a necessity. The
usual color media are molded glass, plate glass, gelatine,
acetate, and mylar. These color media are produced by a
number of manufacturers and the nomenclature of the
individual colors produced by the different manufacturers
is as arbitrary as the type of material. The efficiency of
transmission of light passing through the materials is not
referred to in the present nomenclature. [See Batcheller's
Article, Ed.]
It is a recognized fact that in many industries there is
standardization of materials according to size, etc. Lumber sizes are regu larized as to the type of measu rement
and so ordered regardless of the source of supply. The
same can be said of screws, bolts, nails, costumes, and
many other items used in the performing arts trades. Itis,
therefore, the purpose of this paper to recommend the use
of a standard numerical coding system for color media
that would indicate, 1) the color hue of the material, 2)
the transmission factors, and 3) the type of materials.

this idea of defining color and recommended accurately
determined color components calculated from a theoretical chart by means of three sets of numerical coefficients.
Since the chart represents certain general mathematical
relationships, not all points indicate observable colors and
the three chosen points represent theoretical colors from
wh ich the real color values are computed. "2 These primary colors are recognized by the symbols X for red, Y
for green, and Z for blue. Since three colors are involved,
the mathematics is related to what is termed threedimensional.
A convenient way to illustrate mixing of colors is to
employ a two-dimensional curve, or dome, usually called a
chromaticity diagram, with the three primary colors located at the three points of the curve (Figure 1) with the
"white" source located somewhere inside the dome. The
bottom of the curve represents those colors not in the
spectrum (shades of magenta and purple). The spectral

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Advantages of such a coding system wou Id be, 1) Better definition for the layman of what the material is and
what it will do, 2) Uniform designation of type of materials, 3) Accurate designation of color, 4) Indication of
transmission efficiency, 5) Comparison of colors between
different types of materials as well as between manufacturers, and 6) Aid in finding the missing visible colors that
could be produced.
To determine what method should be used in defining
color, individuals from National Bureau of Standards,
University of Rochester, General Electric, Kopp Glass,
Corning Glass, Kollmorgen, and others were consulted.
The unanimous recommendation was that the internationally recognized Tristimulus Method adopted by the
C.I. E. 1 be used. Other defi nitive methods are widely used,
but only this method is universal and would appear to be
of the greatest value to the layman. Therefore the Tristimulus Method was employed for this proposed coding
system.
The Tristimulus Method is based on the theory that
any visual color tone can be matched by additive mixing
of the correct proportions of the three primary colors
(red, green, blue), provided these three primary colors are
accurately defined. "In 1931 the C.I.E. officially adopted

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