Justodrem exposure meter.
Category
Photographic technology
Date
1935 - 1940
Materials
Metal, Plastic, Glass, Card
Measurements
65 x 40 x 25 mm
Collection
Fox Talbot Museum, Wiltshire
NT 1525834.1
Summary
Justodrem exposure meter. The whole is a simple cylinder with an eyepiece at one end and an aperture at the other. The bulk of the barrel is fixed and shows a table of aperture settings and shutter speeds. Close to the eyepiece is a moveable collar which corresponds to the letters with in the meter. This meter works by using the eye to find the correct exposure. You look through a tube in which a row of letters is glued. The light coming in through the other end of the tube is only bright enough to see a certain number of letters. The darkest letter that can still be distinguished is then looked up on the meter's table to find the corresponding correct exposure. Instuctions for use found on line. Instructions for Use. Setting or Sight. Place the Justodrem close against the eye and slide the outer tube in or out until the letters appear sharp when looking through the meter. Testing Light. Having adjusted for your sight as above, point the Justodrem to the subject. Starting from the brightest letter A, decide which is the faintest letter that is Readable (Test should take 5 to 10 seconds). Observation of this letter forms the test. In the column (on the outside of the meter) under this letter will be seen the various times of exposure (black) for every stop (red). Speed of Film or Plate. Without Filter : Turn the ring (under the eye-pice) to bring the red arrow opposite the Scheiner No. of the plate of film being used. With Filter : Instead of the arrow, set the factor (2, 4, or 8) of the filter opposite the Scheiner No.