Alphonse-Louis Poitevin (1819-1892), French chemist, photographer and civil engineer whose interest in photography arose from the publication of the Daguerreotype process. The basis of his research was to devise a system of producing multiple images from a single exposure. He made a major contribution in the development of photolithography, introducing a system based on bichromated gelatine in 1855 which he patented and started a small photolithographic printing firm in Paris producing plates for several publications. He also patented the collotype process.