Fotogram Exposure Calculator

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Disc calculator for interior and exterior exposure. To be used with early cameras to determine the scene brightness. Obverse has label and curved window for viewing exposure time settings against aperture settings for different times of day and different seasons. Reverse has table of plate speeds and their use for different subject (light) conditions.

Ensign Posometer is a Slide chart, circular, exposure calculator, three concentric disks with inner disk rotatable against outer pair which are strapped together. Celluloid.

Our calculator was kindly donated by Julian Bryant.

Date : 1930

Manufacturer : Fotogram

Physical Description : Calculator disk

This exhibit has a reference ID of CH22006. Please quote this reference ID in any communication with the Centre for Computing History.