Theatre Design & Technology - Summer 1975 - 28

TECHNICAL REPORTS

DAVID HALE & FRED M. WOLFF

STYLIZING SLIDE IMAGES: PHOTOGRAPHY THROUGH
PATTERNED GLASS TO MODIFY SOURCE MATERIAL
GREGORY DEHM
One of the most frequent responses to a recent
student-designed multi-screen projection demonstration at Indiana University was, "Why wasn't there
more stylistic unity in the projected transparencies?"
The criticism was well founded, for despite the
appropriateness of the slides' subject matter, their
diversified formats and contents were not stylistically
unified. Such common methods as dyeing the
slides', out-of-focus copying, or vignetting did not
provide a satisfying treatment and were also too time
consuming within the limits of the schedule. Techniques were sought which could quickly, simply and
economically alter images for projection before their
recording on film. To add the unifying stylistic touch,
a sort of transparent overlay seemed a viable
solution, not unlike some of the relatively expensive
linen and cloth weave negatives available from
photographic supply houses. Due to its low cost and
wide range of design styles, decorative glass was
investigated as this overlaying medium for optical
mod ification.
GENERAL CONCEPT OF THE TECHNIQUE
The basic approach to the process was to add, to
distort, or to modify an image for projection, by
utilizing the optical differentia of glass types and
styles laid upon the subject. It was hoped that the
optical qualities of the glass - causing absorption,
diffusion, diffraction, and other aberrations - would
affect both the incidental and reflected rays hitting
and bouncing off the opaque below the glass. By
laying the patterned sheets of glass directly over the
selected subject matter (pictures, drawings or photographs) and by employing standard photographic
copying or enlarging techniques, the images would
be modified enough to create unique effects without
distorting the original image beyond recognition.
Thus the resultant slide transparencies would be
stylistically unified without gross exaggeration of line
or color.
GLASS: PROCUREMENT AND LlMITA nONS
Obtaining the glass was a matter of choosing from
available sources. Small waste pieces were freely
given by local dealers. A more selective method was
to write directly to a glass manufacturer whose
products were particularly suited to our work.

The industrial term for this decorative glass is
"obscured" glass. We explained our objective and
asked for samples of the product; in most cases, they
were glad to oblige. 2 Since other uses for the
samples were anticipated, all conceivable limitations
and potentialities of the glass were considered in
examining the samples received.
1. It was important that the glass have a high
coefficient of optical transmission. More detail from
the subject was reflected toward the lens of the
camera when less light was absorbed in the glass.
Samples with high levels of transmission were
therefore more suitable for overlay photography.
2. An incomplete or low diffusion level was critical
in the glass when minimal modification of the picture
was desired in order to retain the detail of the image.
3. The qualities of some types of glass produced
diffraction patterns, appearing as parallel light and
dark (sometimes colored) bands. Through the careful
selection of the image to be reproduced, spectacular
overlay effects were created. However, samples with
high diffraction qualities had to be specially requested, as these were difficult to locate at random.
4. Color saturation was an important factor. A
highly saturated color in the modifying medium
absorbed the incidental light, causing poor reflection
of the subject beneath the glass. A slight to medial
color additive eften increased the effectiveness of the
transmitted image, adding an even tone of background color, yet allowing the image information to
remain intact. Of course, any surface could be
mod ified by color with the use of transparent color
media.
5. Heat factors needed to be considered. Though
the overlaying of glass on photographs did not
require high thermal resistance, future investigations
using the samples in place of projector slides were
probable. It was therefore specified that the glass
have a heat resistance at least equivalent to that of
pyrex.
6. The size of the sample for overlaying was not
critical, as long as minimal dimensions covered the
subject adequately. With the variety of pictures
used, it was found that 5" x 5" samples were
sufficient for our present needs. But since future
investigations involving the obscured glass as pro-

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THEATRE DESIGN AND TECHNOLOGY

SUMMER, 1975

Table of Contents for the Digital Edition of Theatre Design & Technology - Summer 1975