mits restitution from reduced uide angle as uell as from 12G° 
photography. 
In order to avoid unwieldy dimensions in this universal instru 
ment resulting from the analog reconstruction of the geometry of 
ultra uide angle photographic rays, the A9 has been designed for 
restitution from diapositives reduced in an optical diapositive 
printer to half the format of the original 9" x 9" negatives. 
Mention has already been made of the U3 + U4 Diapositive Printer 
when making the reduced diapositives, and of the use of cor 
rection plates in the Printer for rational elimination of the 
various "distortions"present in the RC9 negatives. 
The diapositives are centered on their picture carriers over 
a light box and with the help of magnifiers. The focal length 
is set in the two plotting cameras to D.D1 mm by cranking; no 
parts are exchanged for the different (reduced) focal lengths 
of ultra uide or uide angle photographs. The external orienta 
tion elements in the A9 are ", CO 1 , CO", if ', if ", b, by', by", 
bz 1 and bz". The base is set to 0.01 mm by cranking, the 
carriages of the tuo plotting cameras thereby being moved 
symmetrically inwards or outwards on rails on the upper frame 
of the instrument. 
The optical system has the same characteristics as that of the 
Wild A7 : orthogonal viewing through microscopes moving parallel 
to the diapositive plane, short distance from the small black 
measuring marks to the diapositives, left-right image inter 
change for bridging with "base out" and "base in", Dove prisms fo 
left and right optical trains, adjustable eyebase, wide-angle 
lDx eyepieces and squint correction. 
The floating mark is controlled in plan by free-hand movement 
during relative orientation and by two two-speed handwheels 
during operation. The x and y coordinates are read from six-digit 
counters directly to 0.01 mm. Elevation movements are controlled 
by a foot-disk, and direct elevation readings in feet or meters