He and his wife Hansel Mieth were part of the school of socially conscious documentary photo-journalists that included Dorothea Lange, Imogen Cunningham, Peter Stackpole and Robert Capa.
Hagel's photographs of waterfront workers are the basis of two books published by the West Coast ILWU[clarification needed]: Men and Ships: A Pictorial of the Maritime Industry (1937); and Men and Machines: A Story About Longshoring on the West Coast Waterfront (1963).
[citation needed] Hagel and Mieth photographed the inside of the Heart Mountain Japanese American internment camp for Life magazine in 1943, but the photographs were not published by Life, In the 1950s, the couple was blacklisted for refusing to testify before the House Un-American Activities Committee.
[citation needed] Hagel and Meith bought a working ranch in Santa Rosa, California in 1941, and raised chickens for some years.
[citation needed] In 1955 Edward Steichen selected Hagel's high-angle flash-lit photograph, of social scientist Paul Schuster Taylor (husband of Dorothea Lange) conducting a seminar in labor economics,[1] for the world-touring Museum of Modern Art exhibition The Family of Man, seen by 9 million visitors.