(11) 
Canada 
Neither of the cameras to be described for Canada is of recent origin. How 
ever, they have not been described before. 
I he Fairchild K17B camera made by the Fairchild Camera and Intrument 
Corporation has been modified in Canada to make it suitable for photogram- 
metric use. These modifications, described by Nodwell and Burstow 1 , provide 
a framework rigidly attached to the camera cone which defines the film plane 
and supports the fiducial marks. It reduces the picture size to 8f" x 8£". 
Fig. 1 Theodolite camera. A version which mounts above the telescope of the Wild T2 transit 
is also used. 
A theodolite camera used for obtaining ground control in mountainous 
terrain is shown in Fig. 1. It was originally designed and built by the National 
Research Council of Canada in co-operation with the Topographical Survey 
Branch. The camera’s characteristics are as follows: 
Weight 
Outside dimensions 
Lens 
Plate size 
Filter used 
Instruments photographed 
2,\ pounds 
6-| x 4§ x 5* inches 
Ross W/A Anastigmat 112 mm, f:16 
3 1 " x 4T" 
Wratten 88A 
a numbering device 
The glass plate is held against the surfaces defining the focal plane by a spring- 
loaded pressure back. Exposure is by means of a lens cap for the model shown. 
The two 6" wide angle survey lenses used in Canada have been found to 
have an average resolving power of about 9 mm -1 at f:6-3 for annulus taigets 
with difference of log brightness 0-20, mean noon sunlight illumination with 
minus blue filter, and Kodak Aero Super NX film developed in D-19 to a gamma 
of 1-4 as described by Howlett 2 . ( ollimator focal length used is 36 inches.