Theatre Design & Technology - May 1967 - 15

Again the lack of significant differences is much more apparent if one compares the impact of the SF,56 spotlight
at the axis and at two inches from the axis. While there is
an increased change as one shifts from amber to lavender
to blue, even the blue samples in Trials 1 and 2 more often show stability than variability. However, the use of the
optical axis as a measuring point, as against 2" from the
center, will result in more extreme results. In the case of
one dark blue sample, part of the media was reduced to
an opaque black (which can be deduced from the very low
transmission in the blue area of the profile, Fig. 4.15).
4. Comparison of Media at the Axis and Two Inches
from the Axis: SF. 56 and EP.78 instruments
The above comparison was further extended by repeating
the same exposure of media using ell ipsoidal reflector spotlights (EP.78) in Trials 1 and 2. This experimental variation
also impresses one with the similarity between effects at
the axis and at two inches off the axis. It must be remembered that only two extremes are being compared here:
the effect after exposure at two locations, relative to the
axis, in the case of a SF. 56 and of an EP.78 instrument.
In twelve cases out of twenty no significant variation beyond the allowed 10% magnitude of error is observable
(Fig. 5.6, 5.11, 5.15, 5.16, 5.18, to 5.20). An examina-

5.3 Special lavender
Trial 1 - RL842{RL 120)
abc & d- 18 hours

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5.9 Dark blue, Trial 1- CX 19
a,b-18 hours, c.d.-36 hours

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5.8 Medium blue, Trial 1-RL
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5.5 Pale lavender, Trial
CM36 a & b- 18 hours
c & d· 36 hours

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This trial was designed to give a time-lapse portrait of the
process of "burnout" in graph form. The range of 27 hours
was shown by the earlier trials to be sufficient time, the
variables of unexposed and exposed media taken at the center and off-center, and of spherical and ellipsoidal reflector
spotlights also served to show once again the similarity of
effect on the media under similar conditions.

5.4 Pale lavender, Trial 1
CX36 a & b·18 hours
c & d- 36 hours

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tion of Trial 1, Fig. 5.6, and Trial 2, Fig. 5.11 and 5.15,
will reveal the more significant variations. There is a consistent tendency for the spherical reflector spotlights to be
identified with poorer color transmission, a lower spectral
luminance. Fig. 5.15 illustrates this both in the transmission of blue and the absorption of the neutral colors in a
lavender sample. Because the variables in this comparison
(type of reflector, wattage of lamp, and lens type and size)
are so numerous, it is impossibl e to separate the causes of
these differences in the light areas. Finally, the fact that
the other charts in this series reveal little significant change
despite the accumulation of four profiles on each, reduces
the impact of the above differences. To put it another way,
it is relatively true that the conditions for color media holding for one instrument and set of conditions can be applied
to other related ones.
5. Three - Hour Interval and Cumulative Record of
" Burnout"

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