OPTICAL AND SENSITOMETRIC DEVELOPMENTS* 
Paul L. Pryor, Chief, Physics Branch, Photo Reconnaissance Laboratory, 
Wright Air Development Center, U.S.A. 
Abstract 
Recent advances in methods of photographic image evaluation are outlined, along 
with a brief description of the new instruments and equipment designed especially for 
the U. S. Air Force in carrying on this work. These improvements have resulted in MIL- 
STD-150, a document which standardizes most photographic test procedures. The use 
of electronic computers for developing ray trace data is shown to be highly desirable. 
New optical and sensitometric developments are discussed and improvements in film 
processing for night photography are mentioned. The use of electronic and electrostatic 
image forming devices for aerial photography is described briefly, offering savings in the 
requirements for film and equipment weight in aircraft. 
The work is primarily under the direction of the Physics Branch of the Photo 
Reconnaissance Laboratory. 
F IGURE 1 is a photograph of what, in the final analysis, has been the subject 
of a great deal of controversy and study in recent years. It may not be 
readily recognized as being a photograph of a star image; i.e., an enlarged picture 
of an off-axis image of an extremely small point object—the building block of 
optical images. Although this star image can tell a story to the expert about 
chromatic aberrations, coma, astigmatism, etc., it can not be conveniently used 
for making measurements of performance or writing specifications. 
Fig. 1. Photograph of star image. 
Much work has been done recently in image evaluation and improvement, 
as well as in studying the sensitized material on which the image is recorded. 
For many purposes, the resolving power target is a useful device with which to 
* Prepared for Seventh International Congress. Permission for publication granted by Inter 
national Society of Photogrammetry. 
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