PHOTOGRAMMETRIC ENGINEERING 23 
I he method ot application of variable contrast paper to each type will be 
described. 
Figure 3 shows the Air Force Type ¿-14,4 printer adapted for use with vari 
able contrast paper. I he adapter kit consists of a striated filter, installation 
parts, and a set of tungsten bulbs of 3-watt size. 
After installation of the filter kit, the operator changes the color of the print 
ing light by turning a control knob on the front of the printer. This moves one 
filter with alternate blue and yellow filter stripes on a glass plate over a second 
glass plate carrying alternate opaque and clear stripes. As the plate with the 
color stripes moves over the shutter plate, either all blue light, all yellow light. 
or any proportionate mixture of the 
two is transmitted to the sensitized 
material. 
Figure 4 shows the Type jB- 15^4 
projection printer equipped with a 
filter wheel which carries up to 10 
different filters ranging from blue 
to yellow. The operator rotates the 
wheel to select the color filter needed 
to produce the desired contrast re 
sponse from the variable contrast 
paper. 
Figure 5 shows the Air Force 
Type C-\B printer. The accessory 
equipment designed to permit the 
use of variable contrast materials with 
this printer is not yet in production. 
In principle, two separate lamps-—- 
one filtered blue and the other yel 
low-—each direct light into the 
printer aperture. A separate control 
box, to be used beside the printer, 
contains counter-opposed rheostats. 
The operator turns a single control 
knob to effect a simultaneous in 
crease in voltage on one lamp and a 
decrease on the other. This change 
in color is effected without materially 
changing the over-all intensity of the 
printing light. In a continuous man 
ner he can change the color of the 
printing light as he sees negatives of different contrast enter the printer over 
the viewing roller. 
Figure 6 diagrammatically shows the Type D-1 printer. In a semi-automatic 
manner this printer contact prints 9"X9" or 9"X18" negatives onto 1,000-foot 
rolls of paper at rates of up to 20 prints per minute. The printing head contains 
a striated filter which is manually operated as was described for the ¿-Type 
printers to cause desired contrast change with variable contrast papers. 
The experimental model of the Type E-1 printer is shown in Figure 7. In a 
similar mode of operation to that of the D-1 printer, the E-1 also prints at a 
rate of up to 20 per minute 9" X9" prints, though by projection, from any of four 
different sizes of negatives. By means of different lenses, the E-1 will make prints 
Fig. 5. USAF Type C-IB Continuous Printer.