Portrait of Louis Jaques Daguerre, (1789-1851), French chemist and photographic pioneer and inventor of the ???aguerreotype?? From the1820s, partly in conjunction with the French physicist and inventor Joseph Nicephore Niepce, he devised a process which produced directly positive images on a copper plate that had been coated with silver iodide and which, after exposure, produced a positive image by exposing the plate to mercury vapour. By 1837 he had found a chemical treatment to make the image permanent and made public the details of the first widely used photographic process in 1839.