Theatre Design & Technology - Oct 1972 - 14

A COLORIMETRIC STUDY
OF STAGE LIGHTING FILTERS
DAVID R. BATCHElLER, University of North Carolina at Greensboro

The systems and theories concerning color and color
vision derive from the same source. All are based on the
function of the three primary colors of light. The textbooks on stage lighting refer to the Additive Method of
Color Mixing, color scientists refer to the C.I.E. color
order system and psychologists refer to the YoungHelmholtz as the theory which best explains color vision.
These theories and systems are based on the premise that
white light can be produced by mixing the primaries in
equal proportions. It follows also that a given color can be
produced by a properly proportioned mixture of the primaries or their derivatives, the secondary colors. Finally
the premise establishes that two complementary colors
when directed from separate sources produce white light.
The usual approach to color selection in stage lighting
is based on the so-called warm-cool theory. That is, dimensionality will be achieved when two instruments are
cross-spotted one projecting a warm color, the other a
cool. Such is the application of contrast. But there is a
more fundamental contrast that tends to be overlooked; it
is the contrast of complements. In actuality, most of the
cross-spotting conceived in terms of the warm-cool theory
are close if not exact complementary contrasts.
Theoretically, yellow and blue are complementary
colors; these two are the most frequently employed in
creating realistic illusionism. These are also the most abundant colors produced by the manufacturers of stage lighting filters. Except for bastard amber and special lavender,
a few pinks and some greens, no other combinations are
quite as effective particularly for lighting the acting area.
The combi nations that are used tend to be constantly
repeated as lighting designers have little to rely on beyond
additive mixing, the warm-cool theory and their own experience. There is a lack of data connected with stage
lighting color media to supply the designer with more
information than his senses can give him. While stage lighting is and should remain an art, the data obtained by a
colorimetric examination provides the designer with information which all the experience in the world will not
provide.
Not only is the human eye non-selective but an inac-

curate system of color description has developed by association with the visual sensation produced by light. Accurate color specification can be made only by measurement. Colorimetry is the science of color measurement.
Applied to stage lighting, it provides the designer with
brightness percentages, transmission percentages, dominant wavelength, and chromaticities of the colors he uses
to alter the white light produced by his instruments.
These factors are provided in an appendix following the
discussion. It is assumed that the reader is conversant with
the dimensions of color in light (hue, saturation and
brightness) and that the principle of absorption is no
mystery.
Basic to the science of colorimetry is the unit of measure. Light is everywhere about us existing as a form of
energy. It is one of a number of forms of radiant energy,
emitted in all directions from a source. The different
forms of radiant energy are identical in every respect except in wavelength. Therefore, each form of energy possessing a particular distance between wave crests and a set
frequency of oscillation can be placed, according to this
difference, in a pattern which is known as the "electromagnetic" or "radiant" spectrum. This spectrum is composed of all forms of radiant energy which produce a
continuous series of infinitely different wavelengths (figure 1). Each form of radiant energy has its place in the
spectrum according to the length of its waves; the short
gamma rays are at one end and the longer radio waves at
the other.
The forms of radiant energy in the spectrum are measured by their wavelengths. Due to the vast differences
between the longer waves and shorter ones, a series of
interrelated measurements must be used. Radio waves are
measured anywhere from 30,000 meters to 3 centimeters
while some of the shorter rays (light waves, ultraviolet
radiations) if measured in the same unit size would be
represented as one billionth parts of meters. For minute
measurement, science has assigned to wavelengths of light
and other shorter wavelengths, the term angstrom unit
symbolized by A.U. (1 A.U. equals 1/10,000 millimicron).
The millimicron (mu) or nanometer (rim) is also a frequently used unit of measure and is employed in this
discussion. One mu or nm is equal to 1/100,000 mill imeter.

THEATRE DESIGN AND TECHNOLOGY

OCTOBER. 1972

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