Born to Elin Agata (née Nordin) and Johan Viktor Albin Hessner on 13 August in Östersund in central Sweden, Rune Hassner took up photography in 1942.

[4] At the age of 21, like many other young Swedish practitioners, he traveled to Paris and was there for eight years as a freelance photographer undertaking reportage and press work, specialising in the subjects of culture, politics and fashion.

Tired of working in the studio with the camera on wheels, with a lot of lamps, with large format negatives, retouching and smiling for the public, the opportunity and freedom to observe the real face of the people on the street drew me.

"[20] In December 1955 he flew to New York and then, in February 1956 to Hawaii to work there as a stills photographer on a documentary film production,[21] and in June traveled in Central America via Puerto Rico, and to India, USA, Australia and Asia.

In common with many other photographers of his generation and in the group Tio fotografer, Rune Hassner switched from still photography to film when the Swedish and international picture magazines which had sustained their practice were gradually displaced by television.

His work in film was a direct continuation of his photo reportage;[28] from 1965, in his late thirties, Hassner produced many documentaries for Swedish television, including programs on photographers Rolf Winquist and Brassaï.

Like the emerging documentarians, the Briton Richard Leacock and American Pennebaker, Hassner used light camera equipment to produce the 1966 travel documentary of the carnival in Trinidad, Jump up.

In the same spirit, in 1969 Hassner made Bilder för miljoner, an extended documentary series on the history of mass-produced photographic art, emphasising its socially critical function, and as a political weapon.

"[12] They followed that with Hjalparen (1968),[6] and in 1978 collaborated on six films about China for Swedish television,[31] Myrdal having dedicated his book Chinese Journey, photographed by his wife Gun Kessle,[32] to Hassner in 1965.

[33] Hassner flew to New York to speak alongside Ralph Morse, Ken Heyman, Milton Greene and Wayne Miller at the annual Photojournalism Conference at the University of Miami in April 1960,[34][22] and in February 1973 again presented in the United States, in a panel 'Photojournalism: A Matter of Life and Death' with Richard Olsenius and R. Smith Schuneman in conjunction with the exhibition "Margaret Bourke-White: Photojournalist" at the Walker Art Center.

Naomi Rosenblum notes that in developing collections at the University, Hassner "encouraged interest in the history of American and European photojournalism and social documentation through his extensive curatorial, research, and publishing activities.