G VI 1-4 
PHOTOGRAMMETRIC ENGINEERING 
Source Materials for the Photographic Interpreter 
Developments in cameras and photography are the responsibility of other 
commissions of the International Society. Therefore only brief mention will be 
made of the effects of a few recent developments on photographic interpreta 
tion. 
1. ADVANCES IN CAMERAS AND EMULSIONS 
During the past four years there had been considerable progress toward the 
providing the high quality photography needed for detailed interpretation. Of 
particular interest has been the steady advance toward higher-speed, finer- 
grain emulsions. In general, it may be said that, with the lenses and films now 
available, image clarity and sharpness appear no longer to be the major limiting 
factors in interpretation. It might also be noted that certain of the thorny prob 
lems which still plague the photogrammetrist (such as stabilization of cameras, 
and the lack of film flatness) are of somewhat less moment to the photographic 
interpreter. 
2. ADVANCES IN PHOTO-PROCESSING AND PHOTO-MATERIALS 
There have been a number of developments in the photographic field which 
are being used to advantage in photographic interpretation work. A few are 
cited briefly below: 
a. The development of automatic-dodging printers: While quite new, the elec 
tronic type of printer has demonstrated that it can produce materials of the 
tonal gradations and contrast best suited to photographic interpretation. Since 
tone and contrast are important clues in the interpreter’s problems, the value 
of such controlled printing should not be underestimated. 
b. Increased use of “dry” (diazo-type) reproduction equipment in photographic 
interpretation work: By simply and rapidly reproducing annotated photographs, 
overlays, and report materials, this equipment enables the interpreter to dis 
seminate the results of his work in graphic form, rapidly and efficiently to the 
user. 
c. Development of special plastic bases for photographic mosaics and photo 
graphs: Now being used are photo bases serving both as direct viewing positives 
and reproducibles. Mosaics or prints reproduced on this material can be viewed 
directly with reflected light, marked on with ordinary pencil (which can then 
be erased), viewed over light tables as positive transparencies, and placed in a 
printer for reproduction of a duplicate negative. Expanded use of these prod 
ucts may contribute greatly to the flexibility of the photography or photo-map 
as a base for planning and operations in many fields. 
Photographic Interpretation Equipment 
summary 
The basic tools of the photographic interpreter are still the stereoscope, the 
magnifier, and the measuring scale. Depending on the individual and the type 
of interpretation he performs, the interpreter may also employ a variety of 
other aids and instruments. The period 1952 to 1956 was one of increasing 
emphasis on photographic equipment of all types. 
TRENDS 
The following apparent trends were noted: 
1. Apparently a greater utilization, in photographic interpretation work, of 
photogrammetric-type equipment, such as stereo-plotters, comparators,