(October 22, 1912- March 15, 1999) became interested in photography in 1938 when he took it up as a hobby and was encouraged to pursue it as a career when he came in contact with Ansel Adams at the Detroit Photo Guild in 1941. At the invitation of Moholy-Nagy he moved to Chicago in 1946 and began teaching at the institute of Design. While at the Institute of Design Callahan and his friend Aaron Siskind formed the teaching partnership which defined the personality of the school in the 1950’s and educated many important contemporary photographers. He remained in Chicago until 1961 when he joined the faculty of the Rhode Island School of Design. In 1973 he retired and began to devote his time to travel and the pursuit of his own personal projects. A major retrospective of his work was held at the Museum of Modern Art in New York in 1976. He has been awarded Guggenheim and Graham Foundation grants to assist him in his work and in 1978 he was chosen to represent the United States at the Venice Biennale.