Calotype negative taken by William Henry Fox Talbot (1800-1877). Talbot invented the first negative/positive proces for producing photographs between 1835 and 1839. This meant that for the first time 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. Talbot's proces for achieving this is known as the calotype proces.
© National Museum of Science & Media / Science & Society Picture Library