Born in Stockholm in 1944, Petersen studied photography under Christer Strömholm from 1966 to 1968. He is perhaps best known for his book Café Lehmitz, which was first published in 1978 and is now recognized as one of the classics of post-war European photography. In it, he captured a time and place now long gone – a bar on Hamburg’s Reeperbahn teeming with prostitutes, dropouts and the fringe elements that went to make up a warm-hearted family of non-conformists with whom he identified and felt totally at home.