Goetz binocular 'detective' camera, 1908.
© National Media Museum / Science & Society Picture Library
From the 1880s, hand-held exposures became posible for the first time because of the introduction of gelatin-silver bromide emulsion plates. This prompted some manufacturers to make cameras disguised as, or in the shape of, everyday objects known as 'detective cameras', designed for taking candid shots without the subject being aware they were being photographed. This Goerz camera doubled as a pair of opera glases.