A Motion Picture Laboratory Sensitometer

This instrument is one giving a time scale of exposure. The exposure scale consists of 21 steps in which the exposure increases by consecutive powers of √2. The modulation of exposure time is accomplished by means of a sectored drum driven by a synchronous motor. Two standardized electric incandescent lamps are provided, one for use in exposing negative materials and one for positive materials. These are mounted in pre-positioned bases, the lamp itself being permanently set in position at the factory so that when the base is placed on its support by means of two dowel pins the filament of the lamp must lie upon the optical axis of the instrument and in register with the distance indicating scale. Standardized dyed gelatin filters are provided so that for positive materials the exposure illumination has a color temperature of approximately 3000°K., while for negative materials the color temperature is approximately 5400°K., approximately matching mean noon sunlight in quality. Electrical measuring instruments for controlling the standard lamps are an integral part of the sensitometer. Convenient guides for positioning the film to be exposed are provided as well as a roll holder for carrying a supply of raw stock. It is estimated that the probable error in exposure does not exceed ± 2.5 per cent.

Print ISSN

0097-5834

Published

1931-10

Content type

Original Research

DOI

10.5594/J05570