Theatre Design & Technology - May 1967 - 8

4. A comparison of spherical reflector and ellipsoidal
reflector spotlights, as they affect media at the axis
and two inches from the axis for Trials 1 and 2.
5. A specific set of results accumulated by aligning
on one graph the spectral variations taking place at
the end of each three-hour period for each of the
fifteen media in Trial 3. (To avoid hopelessly confusing overlapping of lines in this last series, only
those profiles reveal ing significant and easily recorded changes have been selected.)

The general purpose of the experiment and of the procedures is to stabilize as many factors as possible and thus
to expose the effect of light and heat on the color media
under as many normal conditions as possible. A secondary
purpose is to reveal some of the methodology and conditions necessary for an evaluation of color media. To this
end the accuracy of the measuring instruments is important
(Table 1.6.). The.±. 1.0% accuracy of the spectrophoto-

meter combined with a use accuracy between calibrations of
compounded by other possible deviations, such as
operator variations throughout the experiment, voltage fluctuations, slight shifts in standard among lamps and instruments even though new, and the color variants among the
media samples purchased at intervals over an eight year
period, all lead to a possible range of error totalling at
least + 5.0%.

.±. 0.5%

The ability of spectators to detect differences up to 10%
is also a variable. While the human eye is capable of distinguishing quite minute differences under controlled conditions, it is not so likely under the masking complexities of
a normal production in the theatre. There a difference of
10% in perceived luminance might well pass unnoticed.
The exposition of results, then, will be based on the extent
of variations beyond the estimated magnitude of error
(10%), the change in the percentages of transmission of
spectral energy, and the random and consistent relationships
of change, whether positive, negative or inverted.

FIG. 2. Comparison of unexposed color media, 8, 5,
and 2 years old, stored in relatively light-tight containers: trial 1 (summer, '58). trial 2 (spring, '61), and
trial 3 (spring, '64). Only lavender and blue color media
were included in this list; amber revealed no significant
difference after storage.
2.1 Unexposed. Brigham gelatine No. 1 7. Special lavender
Trials 1,2. & 3

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2.7 Unexposed. Rosco gelatine No. 264 (35). Urban
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Medium blue. Trial 2, Roscolene No. 866(37). Dark urban blue
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2.6 Unexposed. Brigham gelatine No.3 7. Dark blue. Trials
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THEATRE DESIGN & TECHNOLOGY

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