GV-92 PHOTOGRAMMETRIC ENGINEERING 
this in obtaining a more pleasing, a more “idealized” portrait. Obtaining this 
distortion is difficult when modeling the portrait by hand, but is easily obtained 
with the new methods. The sculptor's action is like that of the photographer 
when photographing a tall building and he cannot get vertical lines vertical 
and parallel on the film plane of his view camera; he simply tilts the back 
of his camera. Similarly the sculptor, by tilting the film plane of his motion 
picture camera, can distort his contour pictures so that the top portion or the 
bottom portion of his portrait become larger or smaller. All points between the 
top and bottom will be changed in perfect mathematical proportions. This cor- 
rect mathematical change is important, as thereby the pictures retain the best 
possible likeness, which the carver can transfer to the carved-out portrait. 
The most complicated task of the sculptor— successfully idealizing a sculp- 
tured portrait and yet retaining the best possible likeness—can now be done 
by a simple tilting of the film plane of the camera. 
Obviously the more the sculptor idealizes a portrait, the more the likeness 
suffers. Nature mysteriously, yet accurately records man's inner nature in his 
face; this is difficult for us mortals to read correctly. 
In industry these methods should be taken into consideration in the re- 
production of three-dimensional objects which have surfaces that are irregular, 
difficult to measure, and difficult to machine, such as streamlined surfaces on 
planes, boats and automobiles. 
Stereoscopic Medical 
Photography” 
JULIUS HALSMAN, Chief, Photography Division, 
Armed Forces Institute of Pathology 
Washington 25, D. C. 
HOTOGRAPHY, now in its second century, has progressed from the status of a 
pone. to a highly respected and necessary scientific tool. This tool, when 
used in combination with stereoscopic principles and photogrammetrical inter- 
pretation, has become as precise as a micrometer or transit in its ability to 
supply spatial information. 
It would be unnecessary to explain to this Society the advantages to be 
gained by the use of stereograms over the more commonly used two-dimensional 
processes. It will suffice to say that stereoscopic photographs depict structures 
which otherwise could not be illustrated, give a clearer concept of shape, com- 
parative size, perspective, and depth, and reveal detail normally obscured in 
a two-dimensional photograph. In point of fact, many small structures can be 
more clearly visualized in a stereogram than under magnification or with 
the unaided eve. 
While the value of stereoscopic photography is only beginning to be ap- 
* This is one of the papers included in the Report of the Reporter, U.S.A., Commission V, 
International Society of Photogrammetry.