141. Decoudun's Visual Exposure Meter, c. 1888
Signed: 'DECOUDUN'S PHOTOMETER / PATENT N113,332 / PARIS / LONDON STEREOSCOPIC & PHOTOGRAPHIC Co Ltd'.
Optical extinction meter which measures the brightness of the image on the camera's ground glass focusing screen. The printed table is for converting the meter setting to exposure time standardised for gelatin bromide paper.
Diameter 65 mm, depth 10 mm.
Inventory no. 84,502.