The Collaborative International Dictionary
Photographometer
Photographometer \Pho*tog"ra*phom"e*ter\, n. [Photograph + -meter.] (Photog.) An instrument for determining the sensibility of the plates employed in photographic processes to luminous rays.
Wiktionary
photographometer
n. (context dated English) An instrument for determining the sensibility of the plates employed in photographic processes to luminous rays.