Voigtlander Daylight Exposure Calculator (English)
Exposure Calculator in English
Exposure Calculator (1938).
Cardboard sliding rule giving correct exposure time.
One side for daylight uses latitude, month, hour, subject, f/stop, speed of plates or films and state of light, to give the correct time.
The other side for articicial light uses distances from the light to the subjet, light source, subject to be photographied,
reflector (or no reflector), speed of film, to give the correct f/stop.