Stereoscope modified for viewing photographs of different scales 
Description: A mirror stereoscope modified so that the eye pieces may be 
moved to different positions between the wing mirrors (Fig. 4). 
Shifting the eye pieces permits stereoscopic viewing of photographs of 
different scales. Interchangeable lenses are provided to maintain 
images in focus. 
Photointerpretation applications All photointerpretation problems wherein 
photography of more than one scale is used. (Professor Carlos 
Eugenio Magarinos Torres, written communication, 1959.) 
Image intensifier 
Description: An electronic device designed to intensify photographic tone 
differences. These tone differences may be at any part of the gray 
scale. Both 9" x 9" and 70 mm films may be used. 
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Photointerpretation application: Any photointerpretation problem wherein 
tone contrast of adjacent images is significant. 
  
Remarks: Experimental model only. (C. A. Coleman, oral communication, 1959. ) 
Dimens ionally stable films 
Description: Films whose dimensional stability characteristics approach 
those of glass. 
Photointerpretation application: Particularly useful in aerial studies, such 
as in geology, as positive transparencies for stereoscopic viewing and 
as substitutes for glass plates in some plotting instruments. 
Remarks: Available commercially. (J. L. Morgan, written communication, 1959. ) 
Scanning dens itome ter 
Description:  Densitometer (fig. 5) designed to scan areas or selected paths 
across 9" x 9" photographs. May be connected to profile recorder for 
automatic recording of film densities. 
Photointerpretation application: For photointerpretation studies involving 
measurement of magnitude or frequency of tone changes, e.g. for 
differentiating between some landforms. Density measurements may also 
provide a means of objective description of certain landforms. Also 
useful for measuring microrelief and determining elevations by shadow 
measurements. 
Remarks: Available commercially. 
Field stereoscope 
Description: Single prism stereoscope (fig. 1) modified to include lenses 
for magnification of stereoscopic images; folds flat. Lenses of 3, 4, 
and 5 diopters have been used in this stereoscope. 
Photointerpretation application: All photointerpretation involving use of 
aerial photographs under field conditions. 
Remarks: Experimental only. (T. P, Thayer, oral communication, 1960. ) 
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