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The Audio-Visual Handbook
SCREEN IMAGE TABLES
For 35 mm. Filmstrips
The size of the screen image is governed by the equivalent focal length of the lens and the distance the projector is placed from the screen.
The following table applies when double-frame film is shown. This table shows the size of picture (in feet and decimals) obtained on the screen with a given focal length lens at a given distance, using horizontal frames. The proportions are merely reversed when showing vertical frames, therefore square screens are recommended.
Equivalent
DISTANCE
FROM
MACHINE TO SCREEN
Focal Length of Lens
10'
15'
20'
25'
30'
35'
40'
45'
50'
o
3.0 4.6
4.5 6.8
6.0 9.0
7.6 11.4
9.1 13.6
10.5 15.8
12.1 18.2
13.6 20.4
14.9 22.4
4"
2.3 3.4
3.4 5.0
4.5 6.8
5.8 8.8
6.8 10.2
7.9 11.8
9.1 13.6
10.2 15.2
11.2 16.8
5"
1.8
2.6
2.7 4.0
3.6 5.4
4.6
7.0
5.4 8.0
6.4 9.6
7.3 11.0
8.2 12.4
9.0 13.6
6"
1.5 2.2
2.3 3.4
3.0
4.6
3.8 5.8
4.5 6.8
5.3 8.0
6.1 9.2
6.8 10.2
7.5 11.5
7"
1.3 1.9
1.9
2.9
2.6 3.9
3.3 4.9
3.9 5.9
4.5 6.8
5.2 7.8
5.8
8.7
6.4 9.6
The following screen images are obtained from single-frame film at the same distances with given focal length lenses:
3"
2.3 3.0
3.4 4.5
4.5 6.0
5.7 7.6
6.8 9.1
7.9 10.5
9.1 12.1
10.2 13.6
11.2 14.9
4"
1.7 2.3
2.5 3.4
3.4 4.5
4.4 5.8
5.1 6.8
5.9 7.9
6.8 9.1
7.6 10.2
8.4 11.2
5"
1.3 1.8
2.0
2.7
2.7 3.6
3.5 4.6
4.0 5.4
4.8 6.4
5.5 7.3
6.2 8.2
6.8 9.0
6"
1.1 1.5
1.7 2.3
2.3 3.0
2.9 3.8
3.4 4.5
4.0 5.3
4.6 6.1
5.1 6.8
5.6 7.5
Short focal length lenses should be used when pictures are shown through translucent screens, but such screens are not recommended unless absolutely necessary.