APPLICATIONS OF VARIABLE CONTRAST PAPERS TO 
AERIAL PHOTO RECONNAISSANCE* 
Major L. A. Williams, Chief, Printing and Duplicating Section, P.R.L., 
Wright Air Development Center 
AS A background for this paper, a brief history of the evolution of contrast 
H control in photographic printing materials is presented. 
The first attempt at contrast control in the emulsion coating was revealed 
in a patent by Rudolph Fischer in 1912. This patent described the idea of coat 
ing a base with two emulsions; the first sensitive to blue and green and of soft 
gradation, and superposed on this an emulsion sensitive to blue only and of hard 
gradation. The resulting product, though of brilliant conception, did not per 
form well. The two end gradations were very good, but the intermediate grada 
tions produced prints of poor quality. Sensitometric studies of these results 
showed the emulsion to have a broken H & D curve in the intermediate grada 
tion region accounting for the poor quality prints. 
In 1937 F. F. Renwick of Ilford Ltd., England, was granted patents on a 
greatly improved variation of the Fischer method. Renwick mixed a chloride 
emulsion of hard gradation with a bromide emulsion of soft gradation. The 
bromide emulsion was sensitive to blue while the chloride was sensitized to green. 
Since there was very little overlap in sensitivities, the earlier troubles with the 
Fischer method were not perceptible. This type of variable contrast paper is still 
being produced by the Ilford Company under the name “Multigrade.” 
The Defender Photo Supply Company (later acquired by DuPont) intro 
duced a still different type of variable contrast paper called “Varigam” in 
August of 1940. Rowland S. Potter and Seward Hagaman, originators of the new 
product had discovered a new series of sensitizing dyes which would sensitize a 
single emulsion to respond with high contrast when exposed with blue light and 
with soft contrast when exposed with green. This paper has been marketed here 
since 1940 and was used by the U. S. Air Force to a small extent during World 
War II. 
During 1950, the Air Force began an intensive investigation of photographic 
printing papers which included the variable contrast type. This study was 
sparked by firm demands for greatly improved quality of aerial reconnaisance 
photographs along with very high rates of production of those photos. As the 
equipment for accomplishing these gains began to materialize and results of 
field trials were studied, it became obvious that a variable contrast paper was 
essential to the attainment of the new goals for quality and speed. 
Before proceeding with the specific applications of this type of paper to 
printing operations, a brief glimpse of the rather revolutionary changes which 
are taking place in USAF photo laboratories seems appropriate. Studies of the 
reconnaissance photography of the last war as produced in the field reveal 
average production times of 24 to 48 hours time in the laboratory; average 
resolution of from 10 to 12 lines per millimeter; and lower than acceptable 
average quality. Print rejection and reprint rates were high as was waste of ma 
terials. The entire chain of operations in the production of finished prints was 
examined for weak links. The new goals were established. Average production 
time was set at from 5 to 10 hours; resolution as high as possible; quality level 
equal to or better than trade commercial photography; and positive improve 
ments in all other factors. 
* Prepared for Seventh International Congress. Permission for publication granted by Inter 
national Society of Photogrammetry. 
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