Sir John Herschel

Sir John Herschel, distinguished scientist and astronomer, was one of the forefather's of the modern photographic process. Among his contributions to the development of photography were his discovery of the properties of sodium thiosulfate, "hypo," a fixing agent and in early 1839, the production of positive images from paper negatives exposed in the camera. Although he was the first to publish several ground breaking techniques, much of his work was later claimed and patented by W.H. Fox Talbot.
Cameron had a very close friendship with Herschel beginning in the 1830s. He was the subject of many of her portraits and a provider of technical support and advice.