GV-94 PHOTOGRAMMETRIC ENGINEERING 
and disease; and studies of the changes in length and diameter of muscle fibers 
in an effort to determine whether a traumatic lesion of muscle was caused 
by direct injury to the muscle or indirectly by nerve injury. 
The stereoscopic camera which is used for clinical and gross specimen studies 
at the Armed Forces Institute of Pathology is the Donaldson Camera, now 
being manufactured by the Perkin-Elmer Corporation. This camera features the 
utilization of independent variable inter-lens separation and parallax adjust- 
ments which eliminate distortion (Figure 1). Two rhomboidal prisms are 
mounted in front of each of the matched lenses in such a manner that the dis- 
tances between both the upper and lower reflecting surfaces of the prisms are 
  
Fic. 3. Photograph showing power source, camera and chin rest, as 
used for ophthalmic photography. 
variable. Separation of the upper surface increases or decreases the effective 
inter-lens distance, permitting control of depth effect. The separation of the 
lower prism surface determines the horizontal position of the images at the focal 
plane. This allows parallax correction by translation instead of the more com- 
mon convergence and is responsible for the absence of the usual wedge-shaped 
distortion, or keystone effect. 
All scales on the camera (Figure 1-A, B, G), bellows, extension, interlens, 
distance and parallax correction are calibrated and set according to magnifica- 
tion, and the camera is focused by projecting the images of two vertical fila- 
ments originating at "Z7" located in the roof of the double reflex housing down 
to two reflex mirrors that also perform as shutters reflecting this light through 
the lens-prism combination onto the subject. By moving the camera in or 
out by a special control, these two images are vertically aligned end-to-end 
and the camera is then in focus. The projected images of four point source light 
bulbs (Figure 1) are arranged in a rectangle and exactly define the photographic 
area directly on the subject. 
A built-in "strobe" light (Figure 1-D) activated from a separate power 
source is variable and also scaled by means of magnification tables. This lamp 
is so positioned that it is automaticaly centered on the subject when the 
magnification scales are set. 
Itis to theadvantage of the photographic novice that operation of the camera 
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