In 1929, when the trained banker Hans Retzlaff lost his job as a result of the Great Depression, he turned to photography, a skill he taught himself. Following initial activity as a photojournalist in Berlin, he specialized in ethnological subjects for which he travelled throughout Germany and the neighbouring countries. He marketed his photos on a mass scale in the form of postcards he published himself and in magazines such as Atlantis: Länder, Völker, Reisen.
Starting in 1933 he also published photo books, among them Bildnis eines deutschen Bauernvolkes: Die Siebenbürger Sachsen (Portrait of a German Peasantry: The Transylvanian Saxons, 1934), Das Burgenland: Deutsche Grenze im Südosten (Burgenland: Germany’s South-Eastern Frontier, 1939), and Arbeitsmaiden am Werk (Labour Service Girls at Work, 1940). He placed his photos at the service of National Socialist propaganda. His portrait series of craftspersons and other groups of the population are deliberate manifestations of the racial-ideological conception of a biologically determined community. Along with other photographers such as Heinrich Hoffmann, Erna Lendvai-Dircksen, and Walter Hege, Retzlaff was also involved in the making of the inflammatory pamphlet Der Untermensch (The Subhuman). His Berlin studio and archive were destroyed by bombing in 1945. In the post-war period he founded an image archive for art and culture in Tann in the Rhön Mountains.