Experts believe the image, actually a daguerreotype, was created in 1837 by the inventor of the process, Louis Daguerre. The picture, published yesterday by the magazine Etudes Photographiques, is thought to pre-date previously known daguerreotype portraits by three years. The subject is Nicolas Huet, a friend of Daguerre, and a moderately well-known painter of animals and collector of fossils and shells.
Historians previously believed Daguerre's techniques were incapable of producing an image of a human before 1840. The existence of his method, a refinement of techniques used to produce images of inanimate objects by Nicephore Niepce, was not announced until 1839. Niepce's work needed an eight-hour exposure time; Daguerre reduced this to two minutes.
The picture, 5.8cm by 4.5cm, was discovered earlier this year. Marc Pagneux, a collector, who bought it from its discoverer for an undisclosed sum, describes it as the "Turin Shroud of the photographic world".