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shutter speed ranges from 1/50 sec. to 1/800 sec. at a constant aperture 
of f/5 and the aperture range is from f/5 to f/11 with a shutter speed of 
1/800. 
At a terrain brightness of 2200 foot lamberts, for instance, with an ASA rating 
of 80 and a filter factor of 1, the f/11 aperture will be selected with the 1/800 
second shutter speed. Should the terrain brightness decrease, the photometric 
computer operating on signals from the photo cell sensor and the ASA/filter 
factor control, will direct the servo amplifier and associated mechanism to 
increase the size of the aperture. A brightness value will be reached at which 
the aperture is opened to the f/5 position, the effective shutter speed having 
been maintained at 1/800 sec. With further decrease in brightness the aperture 
will remain constant at f/5 and the effective shutter speed will decrease until 
1/50 sec. is reached. With brightness increasing, the reverse procedure will 
occur on computer commands. 
Thus a complex electronic circuit with computer, amplifiers, and feedback 
servos acts to maintain a constant exposure over an 80 to 1 range, the full 
angular field being sampled by the photo cell. 
Synchronized Operation of Cameras 
The option for slaved or independent operation of the two cameras within the 
system is always available at the photographer 1 s control panel. The operator 
can select either camera to serve as master. The master camera will control 
the instant at which exposure takes place so that the mid-points of the two 
exposures shall occur within one millisecond of a single mid-point of exposure 
pulse. Independent operation means that either camera can operate in any of 
the operational modes. 
Image Motion Compensation 
Image Motion Compensation is a means of correcting blurring of a photographed 
image that results when light beams, incident on the face of the camera lens, 
change their angle of incidence during the time the exposure takes place. 
There are various devices for accomplishing this compensation. Generally, 
it is possible to compensate for motion in one direction only, and the forward 
motion is selected as being the most significant. 
In the KC-6A, IMC is accomplished using vacuum to maintain the film in firm 
contact with the platen, while the platen is translated in the direction of image 
motion. A variable speed motor drives the platen through a precision-geared 
train at the correct synchronizing rate to correct image smear, IMC rate 
being continuously variable from 0. 1"/ second to 0. 8"/second.