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C. Objective, diaphragm, shutter, data panel 
The two basically identical cameras are positioned 
symetrically from the center of the base, They are 
equipped with new f/8 objectives, developed by L.Bertele 
under consideration of the experiences gained with high 
efficiency aerial lenses. Optimum correction within 
the range of the visible and infrared part of the 
spectrum, high resolving power, favourable light 
distribution and practically no distortion (distortion 
less than 3 microns) are the prominent features of this 
83° wide angle lens. 
Both objectives are permanently focused to a distance 
of 9 metres (30 ft.), providing a sharp image within 
the range from about 5 to 30 metres (some 15 to 100 ft.) 
even with the widest aperture of f/8. They can be stopped 
simultaneously to f/32 without changing in any way the 
geometric exactitude of the photographic image. 
The Compur shutters permit exposures between 1 sec. and 
1/500 sec. as well as B and T time exposures. Cocking 
of the shutters and exposure setting are done 
simultaneously for both cameras at the control panel 
in the center of the base tube, similar to the setting 
of the diaphragms. 
The shutters are released electromagnetically with 
a synchronization accuracy of 20 milliseconds. Pro 
vision is made for hand triggering of the shutters if 
the battery current should fail. Plash synchronization 
is provided. 
Plates of standard 6.5 cm x 9 cm size are used for the 
negatives; plate holders are also standard (DIN Standard 
No. 4508). They are introduced into the cameras from 
the outside towards the center and pressed to the 
focal frame. 
Besides two horizontal fiducial marks with a distance of 
75 mm in each camera for the restitution of the inner 
orientation during plotting, the following data are 
recorded on both negatives; calibrated focal length and 
left or right identification; in addition the following 
are recorded in the left camera; camera number, a resetting 
three digit exposure counter and a note panel. The exposure 
data are positioned in those corners of the negatives 
where no stereoscopic image is contained. This arrange 
ment has made it possible to forego the use of over 
dimensioned plates without narrowing down or otherwise 
restricting the stereoscopic field. 
D. Viewfinder 
For the azimuthal orientation of the camera towards the 
object to be photographed, the C120 is equipped with an 
optical viewfinder attached to the base tube. In its