Hold the meter at normal reading distance, point toward the subject to be photographed (preferably toward halftones) and look through the lateral opening. Inside the meter there is a row of figures: 32 16 8 4 2 1
Note the darkest figure of this row that you can still read. You will also find this figure on the moveable cellon scale of the meter. Shift this scale until that figure sets on the corresponding field (as explained below) - and all is ready.
Symbols, from top:-
For sunlit distant landscapes, snow and sea scenes set the figure on the yellow-white-blue field
OUTDOORS, in sunshine, use the yellow-white field
In shadow or no sunshine use the white field
In INTERIORS with light walls or with bright artificial light, place the figure on the blue-white field.
In INTERIORS with dark walls or with low artificial illumination, set the figure on the blue field.
If you use a film of 26 degrees Scheiner sensitivity, you will find the correct stops and exposure times lined up on the meter scale without further adjustment. If you want a reading for any other film speed, for instance 20 degrees Scheiner, then simply move the '20' to the place occupied by '26')
The upper row of figures on the cellon scale are the lens diaphragm numbers of the English system, followed to the right by film speed ratings in Scheiner degrees. The middle row of figures contains the numbers of the Continental lens diaphragm system. The figures of the lower row represent exposure times in seconds.
You may now select any stop you wish to use and directly below that stop number find the exposure time in seconds or fractions of seconds.
Example 1. On a sunny day, a scene has to be photographed. The meter reads '8'. Place '8' on the sunshine field (yellow-white) and as best average exposure will be found with 26 degree Scheiner film 1/50 sec. at f/8, or 1/250 sec/ at f/4 etc. For 20 degree Scheiner film, for instance, the exposure would be 1/10 sec. at f/8, or 1/50 sec. at f/4, etc.
Example 2. On a dull grey day a street scene must be photographed. A wall of a house has halftones. The meter gives '8' as the last figure that can just be read. Figure '8' is set on the white field, and as best average exposure for 26 degree Scheiner film results 1/10 sec. at f/8, or 1/50 sec. at f/4. The exposure for 20 degree Scheiner film would be 1/2 sec. at f/8, or 1/10 sec/ at f/4 etc.
For ORTHOCHROMATIC material the exposure time given by the mater should be DOUBLED when working with ARTIFICIAL light. Panchromatic film needs no such increase.
If the speed rating of the film is not known to you, ask your dealer. As it is impossible to produce absolutely accurate and practical figures for the sensitivity of the negative material, it is best to get used to one type of film and not to change without good reason. When a new type of emulsion is used and a row of under-exposed negatives are obtained, it is certain that too high a speed value has been used. If over-exposure results, the opposite has obviously been the case.
The following table gives approximate conversion data for the various systems of speed numbers given by makers of sensitive materials.
Symbol on the Cellophane Scale
Scheiner Degrees
DIN Degrees
H. and D. Numbers
17
17 - 19
7 - 9
100 - 200
20
20 - 22
10 - 12
200 - 400
23
23 - 25
13 - 15
400 - 800
26
26 - 28
16 - 18
800 - 1600
29
29 - 31
19 - 21
1600 - 3200
There is another model of the LEUDI meter available, the LEUDI Cinemeter, with scales specially fitted for all motion picture cameras, for frequencies of 8 to 128 frames per second, and for film speeds from 15 degrees to 29 degrees Scheiner.
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