1911 Encyclopædia Britannica/Claudet, Antoine François Jean
CLAUDET, ANTOINE FRANÇOIS JEAN (1797–1867), French photographer, was born at Lyons on the 12th of August 1797. Having acquired a share in L. J. M. Daguerre’s invention, he was one of the first to practise daguerreotype portraiture in England, and he improved the sensitizing process by using chlorine in addition to iodine, thus gaining greater rapidity of action. In 1848 he produced the photographometer, an instrument designed to measure the intensity of photogenic rays; and in 1849 he brought out the focimeter, for securing a perfect focus in photographic portraiture. He was elected a fellow of the Royal Society in 1853, and in 1858 he produced the stereomonoscope, in reply to a challenge from Sir David Brewster. He died in London on the 27th of December 1867.