-14- 
The automatic exposure control is self-contained in the KC-6A 
camera and operates the shutter and diaphragm with an accuracy of 
t 1/2 f stop. Exposure control is accomplished by automatic adjust 
ment of the shutter speed and the diaphragm opening so that an opti 
mum combination shutter speed and diaphragm opening is used under 
varying light conditions. 
The KC-6A camera generates a pulse at the midpoint of ex 
posure. This pulse freezes all flight data which will subsequently be 
recorded on film. Before the end of the cycle, the KC-6A transmits 
a display request pulse. The data recording equipment then reads 
out to the display generator the data frozen at the midpoint of expos 
ure. The character generator must wait until the film is indexed to 
the next unexposed frame to record the data on the trailing edge of 
the exposed frame. The KC-6A camera signals the character data 
generator when the indexing has been accomplished and the film and 
platen are both stationary. At that time, the computer will begin 
transmitting data to the character generator. Data is formatted for 
output to the image producing cathode ray tube in the KC-6A camera 
in the form of dots arranged in a dimensionally precise matrix. 
This format is illustrated in Figure 6. 
Relative film velocity is controlled by an Image Motion Com 
pensation System which obtains a V/H signal from the AN/USQ-28 
System. The IMC is continuously variable over the range 0. 01 to 
0. 08 knots per foot. The maximum IMC error attributable to the 
camera and its controls are t 2%. The camera can also be operated 
without IMC. 
Figure 7 is a photograph of the first Geocon IV lens assembly. 
This lens is the latest of the Geocon series designed by Dr. James 
Baker. As stated in the specifications of Table 2, the lens is a f/5 
93° apochromatic mapping lens. The lens and lens assembly weigh 
slightly under 40 lbs. It is supplied with both clear and minus blue 
anti vignetting filters for either black and white or color photography. 
Variation and exposure over the film is less than 2%. Actually,