Submitted by Al …
An exposure meter is defined as a photographic auxiliary device that measures the intensity of light under varying conditions of illumination and indicates proper exposure (i.e., the combination of aperture and shutter speed) for film or image sensors of a specific sensitivity.
This exposure meter is British made and is a product of Photax (London) Ltd.
To understand how this exposure meter works, I have reproduced the instructions here:
The Photax Exposure Meter
Open the lid of the meter and a light sensitive scale of numbers 1.4 to 16 will be seen. The purpose of the lid is to protect the scale from dust when the meter is not in use, and also to protect the meter from overhead light when in use.
The figures of the light sensitive scale represent the light values for the corresponding scale above the lid.
Now take the meter into your hand as if reading a book and direct it towards the object to be photographed. Take the last figure which can be read clearly, note this figure, and turn the scale F above the lid until the number found on the light sensitive scale is opposite the degree of sensitivity of your film. The sensitivity values of the films are given on the scale S.
The times of exposure can now be read on the three scales: T₁, T₂, T₃. These three scales represent:
T₁. Outer scale. Times of exposure for outdoor photographs under bright sunlight conditions
T₂. Centre scale. Outdoor scenes, clouded sky or shaded streets. Also for indoor subjects with bright light.
T₃. Inner scale. Dark interiors or under very dull outdoor conditions.
The figures on the three inner scales are as follows:
The red figures are fractions of a second.
The black figures are full seconds.
The white figures on a red field are minutes.
Example 1. A film sensitivity 23° Scheiner is being used and the Figure 8 has been found on the light sensitive scale. Now note the Figure 8 on the ring F and turn this ring until the Figure 8 is opposite Scheiner 23 on the scale S. In case this figure can be seen in a sunlit and bright landscape, the exposure with a lens aperture of F/8 is 1/50th of a second; with F/32 it is ½ a second and with F/2 it is 1/1000th of a second.
Example 2. If the photograph is to be taken under a cloudy sky in the late afternoon and the Figure 4 can be seen on the light sensitive scale, bring this figure opposite Scheiner 23 on scale S the centre scale will then read as follows:
½ second with F/8, 2 seconds with F/16, 10 seconds with F/32
Example 3. When photographing the interior of a cathedral or other dimly lit building and the number seen on the light sensitive scale is 2.8, bring this figure opposite 23° Scheiner on the scale S. The reading will then have to be taken from the inner scale and will be as follows:
F/2 1 second exposure, F/8 15 seconds exposure, F/32 4 minutes exposure.
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