Theatre Design & Technology - May 1967 - 7

srep lens, 400 watt, 6" quartzline spotlight from Kliegl
Brothers, designated ES.46 OK. In each succeeding trial
increasing control was exercised to create a condition approaching normal stage practices. In the second trial all
media were tested at the same time with new lamps: in
addition to this only new instruments were used in the third
trial. Furthermore, (Table 1.4.), the vertical angle was also
changed from horizontal to 45 0 in this trial, the lamp position was focussed from flood to spot, and the power applied was taken from the line source rather than through
the dimmers. Finally, the terminal effect of the "burnout"
was found to approximate 27 hours, and a cooling period
was inserted between each three-hour period of the third
trial. Of most importance was the development before the
third trial of a method for evaluating the degree of "burnout" at each three hour period: a point-by-point record
which was absent in the first two trials (Table 1.5.). In
those earlier trials, footcandle readings were made at such
intervals (Table 1.4.). These were revealing in the overall
variation of light transmission, but failed to pinpoint where
these shifts in the spectrum occurred as the light and heat
affected the color media. However, before and after examinations and comparisons across the three trials were possible
from the samples of color media used.
Before the third trial, even though the instruments were in
excellent condition, footcandle readings were taken to reveal
any inconsistencies in individual pieces of equipment. The
variation among instruments ranged between 185 footcandles
and 210 footcandles. To minimize these differences, samples
of the same color area were assigned to instruments with
similar footcandle readings. After the color media were inserted, the instruments were run at three hour intervals. At
the end of a three hour period, the color medium was removed and a sample one-half inch square was taken from
a point two inches from the center of each color medium.
To prevent the escape of heat through these openings and
to keep intact the delicate gelatine media, each opening
was patched with a piece of equal size taken from the original sheet. Since such patching might cause variations in
the results, a safeguard was provided by using another set
of media as controls in each of five additional SF. 56 K instruments with Brigham gelatine
o. 17, Rosco gelatine
No. 264, Roscolene No. 815, Cinabex No. 36, and Cinemoid No. 19, inserted in these at random. In this control
series only one sample at a time was taken from these exposed media, after 6,9, 12, 18, and 24 hours, respectively.
In an effort to simulate relatively normal production conditions, the instruments were allowed to cool from one and
a half to three hours after each three-hour functioning period. It was judged that if the instruments did not have an
opportunity to cool and the color media were under constant
heat for a six-hour period, the cumulative effect would be
too far removed from normal conditions. As it was, the
three-hour period provided a rigorous test of the media
since few performances last that long with peak output for
most instruments. At the completion of the third trial,
spectral transmittance curves of each sample, as listed
above at the end of Table 1, were obtained from the recording spectrophotometer. On these charts, the horizontal
scale located across the bottom of the page, indicated the
visible spectral wavelength which is measured in nanometers, formerly termed millimicrons. The vertical scale measures the percentage of transmittance of light at each of the
color variations of the visible spectrum. The basic color
areas, as used on all charts in Figures 2 to 6, are presented in Figure 1.7 This illustration is combined with a
curve showing the amount of radiant energy necessary to
produce vision along this spectrum. Reciprocals of the
spectral luminous efficiency, on a scale of 1 to 10 rather
than percentage, indicate "the relative amounts of energy

THEATRE DESIGN & TECHNOLOGY

MAY 1967

I_.

II II

I I
I
I

I
-,

/ I

I
I

FIG. 1. Spectral luminous efficiency in per cent. Color
areas and wave length of radiant energy expressed in
nanometers.

required to produce equal perceived luminances." In this
range the two outer divisions, violet and red, represent a
very low capacity of radiant energy required to produce
measurable visual sensation. In fact most of the visual
sensation is derived from the wavelengths ranging from the
490 to 630 nanometer area (green, yellow, and orange) in
the center of which, at 555, peak luminous efficiency for
photopic (as against scotopic vision) is possible. The three
colors chosen for this experiment cover the spectrum in a
relatively representative range. Amber has its lowest radiant energy everywhere but in the red, orange, and yellow
areas; lavender has high energy levels in the red and blue
areas and depends for its color on relatively low transmission in the yellow and green areas in the center of the
the spectrum; and blue, of course, has high radiant energy
in the blue area but also, in some of the samples, in the
extreme red area from 700 to 760 nm, a spectral range
of low luminous efficiency. These contributions to the total
color of amber, lavender, and blue will be used to evaluate
the spectrophotometric profiles recording the color variations in the respective color media. This will be true particularly for lavender with its three contributing areas, and
blue with its single main area.
On the basis of the three trials described above, the following four general comparisons and one specific one were
examined for significant results:
1. A comparison of the three trials for each of the unexposed colors used in this study to evaluate color
stability. (These samples had been stored in relative·
Iy light tight boxes at the time of each trial and had
aged eight, five and two years. respectively.)8
2. A similar comparison of lavender and blue to evaluate the color stability of the media at the end of
each trial, particularly in relation to variations of instrument angle and focus, in relation to the varying
time periods (18,36, and 27 hours duration), and
in relation to an off-axis color medium sample.
3. A comparison of the effect of Iight at the axis with
a location two inches from the center for Trials 1
and 2.

Table of Contents for the Digital Edition of Theatre Design & Technology - May 1967