United States of America 
Several American cameras were described in the previous Archives. How 
ever, enough new information is available on some of these to justify them being 
listed again here, information is also available on one new camera, the Fair- 
child Ill, and on four other American survey cameras which had not been 
described previously. The available data on these cameras are given in the 
following tables. The Zeiss RMK P-10 is used with Wratten 2 and G filters. 
Camera 
Mark Hurd 
Park 
Aero Service 
Wes Smith 
Lens 
Metrogon 
5-2"or6"f:6-3 
fluorided 
Metrogon 
5-2"or6"f:6-3 
fluorided 
Metrogon 
5 -2"or6"f:6-3 
fluorided 
Metrogon 
6" f :6 -3 
fluorided 
Shutter 
Mark Hurd 
between lens 
1/50-1/300 
Park 
between lens 
1/50-1/300 
Fairchild 
between lens 
1/50-1/300 
Fairchild 
between lens 
1/100-1/300 
Operation 
Manual 
Manual 
Manual 
Manual 
Minimum expo 
sure interval 
8 sec. 
8 sec. 
8 sec. 
8 sec. 
Format 
9" x 9" 
9" x 9" 
9" x 9" 
9" x 9" 
Exposures 
190 on film 
190 on film 
190 on film 
190 on film 
Film held by. . . . 
pressure 
vacuum 
pressure 
pressure 
Lens hood 
yes 
yes 
yes 
yes 
Filter 
minus blue 
graded density 
minus blue 
graded density 
minus blue 
graded density 
minus blue 
graded density 
Instruments 
photographed 
none 
none 
none 
none 
Resolving power of the Metrogon lens is given by various organizations as 14 
to 39 lines per mm, 14 to 56 lines per mm, and 20 to 70 lines per mm. The 
resolving power of the Zeiss Topogon 10 cm is given as ranging from 21 lines 
per mm at the margin to 59 lines per mm on axis. All these resolving power 
figures are apparently based on high contrast multiple line targets. One organ 
ization uses in their tests a collimator of 250 mm focal length. 
The new Fairchild Til camera illustrated in Fig. 5 is not yet available 
for civilian use. Its most important improvement is the new Fairchild Wilcox 
Rapidyne shutter which can be removed from between the lens elements without 
affecting the camera calibration. Another change is the use of artificial illumina 
tion for the fiducial marks, the lens serial number, and the calibrated focal 
length markers. The new magazine contains two separate light-tight chambers 
for the supply spool and the take-up spool and has thermostated electrical 
temperature control to maintain 55 to 60°K