photographer noted for his experimental photography, particularly in colour, and for his contributions to photographic education.

Siegel already had 10 years of experience in photography when he received a bachelor of science degree in sociology from Wayne State University in Detroit in 1937. That same year he was granted a scholarship to attend the Institute of Design at the Armour Institute (since 1940 the Illinois Institute of Technology) in Chicago, which had recently been founded by László Moholy-Nagy (Moholy-Nagy, László). His career as a photojournalist began with The New York Times in the late 1930s, and over the years he handled thousands of assignments for major magazines and news services. In 1946, after several years in the U.S. Office of War Information and the U.S. Army Air Corps, he accepted Moholy-Nagy's invitation to teach and organize a photography workshop at the Institute of Design, becoming head of the photography department.

From 1951 Siegel was involved with experimental techniques. He was a pioneer in exploring the creative possibilities of colour photography, using colour and its variations in tone to express emotional states. The objects in his photographs were often abstracted, so that colour acted as his main expressive component. He exhibited his photographs abroad and in the United States, having two all-colour one-man shows at the Art Institute of Chicago and participating in many group shows, among them Edward Steichen (Steichen, Edward)'s “Image of America” exhibit at the Museum of Modern Art in New York City.

Siegel left the Institute of Design in 1955 so that he could channel all his energies into photojournalism and commercial photography. He edited the book Chicago's Famous Buildings (1965) and wrote many articles on photography. In 1965 he returned to the institute as a professor, and in 1971 he became the president of the institute.