taking its measure

Spring 1948 ad for a GE PR-1 hand held light meter

Toronto. While browsing for photo history material, George Dunbar spotted this May 1948 ad for a GE PR-1 selenium exposure meter and shared it with us. To separate the GE meter from others, it was advertised as having a ‘memory’ long before solid state memories existed. The meter likely trapped the exposure needle when the activation button was released.

Until glass plate and film media became sufficiently sensitive to demand accurate sub-second exposures, photographers managed with experience and notes relating plates, cameras, and light.

When ‘instantaneous’ exposures became common, various ‘calculators‘ and extinction meters were offered. The first true exposure meters were those using a selenium cell to detect the light and convert the light photons into a tiny current. This current usually gave a meaningful number which a calculator could translate into camera settings for a given plate or film sensitivity. The results usually displayed combinations of shutter speed and f/ stop.

Unfortunately, selenium cell light meters were useless after the evening began or to measure ordinary indoor light level. The arrival of CdS cells (which required a battery) solved this short coming. The incorporation of a meter in the camera spelt the end of the hand held meters. And today even translation to camera readings is automatic! That’s the meaning of ‘program’, ‘aperture priority’, and ‘speed priority’ settings on digital cameras.

Note. The title is from a common expression.

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