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PHOTOGRAMMETRY
The circular photographic image produced by the Fisheye-Nikkor is an
exact reproduction on a flat plane of all objects encompassed within the
180° hemispherical
field.
This feature enables the lens to be used in locating
astral bodies or recording cloud distribution. The center of the image cor-
responds to the zenith in the angle of view, and the distance of any point
in the image from this center is directly proportional to its angle from the
zenith,
expressed by the equation y=C0 where y is the distance of the point
from the image center, 6 is the zenith angle, and C is a constant (see below).
For example, a point in the image 4mm from the center represents an object
at an angle of 30° from the zenith in the angle of view. The table below
gives zenith angles for points at given distances from the center of the film
image.
Relation of Zenith Angle to Distance of Point from Image Center
0: Zenith angle
y: Distance of point
from image center
y
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
8°
0.00
3.58
7.17
10.76
14.36
17.98
21.62
25.27
28.95
32.66
36.40
40.17
43.98
47.83
51.73
55.67
59.67
63.72
67.84
72.03
76.31
80.69
85.21
89.97
A0°
3.58
3.59
3.59
3.60
3.62
3.64
3.65
3.68
3.71
3.74
3.77
3.81
3.85
3.90
3.94
4.00
4.05
4.12
4.19
4.28
4.38
4.52
4.76
0°10
o
20
o
30
o
40
o
50
o
60
o
70°80 90
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