Nicolaas Henneman taking a calotype portrait of Pullen, c 1841.
© National Media Museum / Science & Society Picture Library
Calotype by William Henry Fox Talbot (1800-1877). Henneman, previously Fox Talbot's valet, worked with him at his photographic studio in Reading, set up in 1844. Fox Talbot invented the negative/positive process for producing photographs between 1835-39. 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.