NOTES ON THE WILD AVIOGON 
by 
R. David, Heerbrugg. 
(Editor’s note. It is regretted that the supply of reprints of this paper furnished 
in English was exhausted at the Congress. The paper has been reset in type and 
appears herein without figures in the English version. The reader is referred to 
the French version beginning on page (280)-l for figures). 
The Wild Aviogon is a 1 : 5.6 wide angle lens designed for photogramme- 
tric surveys. Calculation has proven its excellent characteristics, defined by a 
high degree of resolving power, very little distortion, and only a moderate 
decline in the brightness toward the corners of the pictures. We propose, in 
this paper, to show that the expectations warranted by the computed character 
istics were fulfilled. 
1. Resolving power. 
The resolving power of the Wild Aviogon was determined by the photo 
graphic method. We used white light and the Gevaert Avi-Microgran emul 
sion (similar to Kodak Super XX) for all pictures. This choice had the object of 
approximating practical conditions as closely as possible. 
Monochromatic light (575 millimicrons) is often used for resolving power 
measurements on fine grain plates. This practice is of interest to the computer, 
to be sure, but hardly to anybody else. Indeed, it is quite useless for practical 
purposes, and tends to give an altogether wrong, and far too lenient, evaluation 
of the lens. Measurements with white light and fine grain plates are the only 
ones of value, for they actually show what the lens can do, with the better 
emulsions. 
We used two types of gratings and a circle for testing purposes. The first 
grating, built into a collimator, consisted of six lines arranged in a square, with 
maximum contrast (infinity). This was used for all routine checkups. 
The second grating consisted of three lines arranged in a square, with 
variable contrast, in accordance to the rules set forth in “A Draft Specification 
of Methods of Calibrating Photogrammetric Cameras”... 1.1.1 and 1.1.2.” 
Since we currently have but one grating of that type, it was used only on our 
prototype, for time was of the essence. It embodies a circle testing object. 
Infinity and Log. 2 were chosen as contrast ratios. 
Two types of collimators were used, namely collimators having a focal 
length of 80 cm (31.5") and the usual arrangement for grating No. 1, and a 
collimator having a focal length of 50 cm (19.69') for test grating No. 2. In 
this instance, the test object is so large that variations (of such characteristics 
as have to be varied) and measurements are easy. The results of these resolving 
power tests are presented in Figures 5 and 6. 
Distortion. 
The distortion was measured visually on a precision goniometer. The dia 
meter of the goniometer circle used was 25 cm (9.84 ), and it was divided into