PHOTOGRAMMETRIC ENGINEERING 
21 
The high-capacity production laboratories of tomorrow will be radically dif 
ferent from those of today. The hand method of print production, sheet by sheet, 
will be replaced by roll type printers. Paper and film rolls will be processed in 
continuous processors and dried simultaneously. I he old bugaboo of equipment 
getting complicated has been faced and it is believed to be licked. Printers and 
processors are rugged machines designed for field operation and maintenance. 
The efficiency of the new roll-type equipment will be monitored by a system 
of I rocess Control Sensitometry developed for field use. The equipment consists 
essentially of a small sensitometer and a processor for sensitometric strips. In a 
simple manner, the speed, contrast and fog of films or papers can be measured; 
the replenishment rate necessary to maintain uniform contrast and density of 
negatives and prints can be determined. 
Air Force laboratory structures are also undergoing changes. Permanent- 
type laboratories for the high capacity production units, such as Reconnaissance 
Technical Squadrons, are being built at bases in this country. These buildings 
are designed for efficient use as photographic laboratories. For mobile operation, 
where rapid moves are necessary by both road and air means of transportation, 
a set of air conditioned trailers has been developed that can be hauled over the 
roads or flown from base to base in transport airplanes. This type of trailer will 
contain the roll type printing and processing equipment installed for operation. 
In combination with field generators, water supply equipment and additional 
shelters, field operation at high efficiency is expected. 
With this brief picture of the new type photo production units in mind, the 
part played by variable contrast papers in this system will be discussed. 
The problems that face Air Force laboratories in connection with printing 
aerial reconnaissance negatives are, for the great part, identical with those of 
the commercial or professional photographer. Acceptable quality prints must be 
produced from negatives which vary in contrast or density range. Within one 
roll of negatives, changes in type of terrain or in lighting conditions often cause 
these differences in negatives. The response characteristics of variable contrast 
paper cause the paper to change in contrast as the color of the printing light is 
changed from blue to green (or yellow). This permits the operator to change the 
color of the light (by changing filters) before printing each negative. With con 
ventional graded papers he must choose one from four or six different papers, 
each with one fixed contrast, to print each negative. The necessity for variable 
contrast papers with Air Force roll-type printers using 1,000-foot rolls of paper 
immediately becomes obvious. It is relatively impossible to pre-select one grade 
of fixed contrast paper which will give acceptable print quality from negatives 
that are of different contrast (density range). Since it is impossible to change to a 
different grade of paper each time a negative of different density range must be 
printed in these printers which use 1,000-foot rolls of paper, the paper must be 
capable of readily changing its contrast to fit all different types of negatives. 
The range of contrasts available with variable contrast paper is shown in Figure 
1 and the range of contrasts available with the four grades of conventional 
printing papers is shown in Figure 2. 
There are five different types of U. S. Air Force photographic printers. These 
must be modified in different ways in order to handle variable contrast papers. 
The five types of Air Force printers are 
Type A—Contrast, cut sheet 
Type B—Projection, cut sheet 
Type C— Contact, roll, continuous 
Type D—Contact, roll, step and repeat 
Type E— Projection, roll, step and repeat