Appendix A - Identifying Kurt Franz Camera
The confident identification of existing buildings imaged on both ground and aerial photos required triangulation to pinpoint the position from which the terrestrial pictures were taken and the angles to the various buildings visible from ground and air stations. For this, a knowledge of the type of handheld camera used is required as well as its nominal focal length, its field of view (Fov), and the format of the film used. Several makes of German cameras produced in the era between 1930 and 1943 were considered. The cameras surveyed are shown in the table below.
|Camera Model/Year||Lens||FoV||Film Format|
|Leica/1930||Hector 50mm f/25||37.6 degrees||35mm film - 24 x 35mm|
|Voightlender Bessa/1936. Folding Belows||105mm f/2.8||46.4 degrees and 24.2 degrees||120 film with two options: 90 x 60mm or 45 x 60 mm|
|Kodak Retinette/1939||45mm f/2.8||40.7 degrees||35mm film - 24 x 35mm|
|Minox/1938-43||15mm||40.1 degrees||8 x 11mm|
The Leica inclusion afforded a generic type for all 50mm focal length, 35 mm film cameras. The other cameras included a variety of formats. The Minox was produced for the German army in WWII. The Voightlander and the Retinette covered commonly produced cameras available to the German public. Of these cameras, analysis showed that only one could have been the instrument used by Kurt Franz: the Voightlander Bessa, a bellows type camera with a relatively long nominal focal length of 105mm. The Voightlander had two modes of operation: one could expose eight 90 by 60 millimeter pictures, or sixteen 45 by 60 millimeter frames. Analysis revealed that the Franz photographs were exposed in the smaller format.