Chudleigh, Devon, c 1843.
© National Media Museum / Science & Society Picture Library
Salt print from calotype negative. Photograph by William Henry Fox Talbot (1800-1877). Fox Talbot invented the negative/positive process for producing photographs between 1835-1839. Any number of prints could be made from the same shot by transferring the negative image on to special paper to make a positive print; these prints were called calotypes.