Harry Morey Callahan (October 22, 1912 – March 15, 1999) was an American photographer who is considered one of the great innovators of modern American photography. He was born in Detroit, Michigan and started photographing in 1938 as an autodidact. By 1946, he was appointed by László Moholy-Nagy to teach photography at the Institute of Design in Chicago. Callahan retired in 1977, at which time he was teaching at the Rhode Island School of Design.

Callahan left almost no written records–no diaries, letters, scrapbooks or teaching notes. His technical photographic method was to go out almost every morning, walk the city he lived in and take numerous pictures. He then spent almost every afternoon making proof prints of that day’s best negatives. Yet, for all his photographic activity, Callahan, at his own estimation, produced no more than half a dozen final images a year. Read full wikipedia article.