A British polymath equally adept in astronomy, chemistry, Egyptology, physics, and philosophy, William Henry Fox Talbot spent years inventing a photographic process that created paper negatives, which were then used to make positive prints — the conceptual basis of nearly all photography until the digital age.
"In Light of the Past: 25 Years of Photography at the National Gallery of Art" runs through July 26: http://1.usa.gov/1HUfi1M.
William Henry Fox Talbot, "A Scene in York: York Minster from Lop Lane," 1845, salted paper print, National Gallery of Art, Washington, Edward J. Lenkin Fund, Melvin and Thelma Lenkin Fund and Stephen G. Stein Fund, 2011
William Henry Fox Talbot was a British scientist, inventor and photography pioneer who invented the salted paper and calotype processes, precursors to photographic processes of the later 19th and 20th centuries. Wikipedia