Abstract
This paper describes a new photographic exposure meter, which measures the brightness of the scene to be photographed. It utilizes for its light measuring element two Weston photronic photoelectric cells connected in parallel to, and mounted in the same case with, a permanent magnet movable coil indicating instrument calibrated in units of brightness: candles per sq. ft. The cells are of the direct action dry disk type, which transform light energy directly into electrical energy, requiring no battery, and having an unlimited life. They are mounted in tubular depressions to limit the area of the scene covered. — A simple mechanical dial calculator attached to the meter case translates light values into exposure values by a single setting of a dial, after having set the calculator once for all for the speed of the film being used. The calculator has the novel feature of providing means for fitting the brightness range of a scene as determined by its darkest and brightest objects, to the correct film range indicated on the dial as lying between the darkest and brightest objects which the film will correctly expose, for the indicated shutter speed and aperture.
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