He discovered his passion for mountains thanks to his readings; in his autobiography he specifically mentions Achttausend drüber und drunter by Hermann Buhl and a book on Everest's ascent by Edmund Hillary.
His mother encouraged him by sending him to the Mountain Club in Heidelberg, where he met Hermann Kühn, partner in several ascents, including the Eiger's north face.
[3] He was part, as photographer, of the same expedition which saw Reinhold Messner and Peter Habeler climb Mount Everest for the first time without supplemental oxygen.
His last mountain was Fitz Roy, which he climbed in 1982 with Peter Luthy on the south-west face (route Chouinard) two weeks after the failed attempt on Supercanaleta.
His books are the following: Karl died on 19 May 1982 in an ice avalanche at Camp II 6,900 metres (22,600 ft) on Cho Oyu, during his attempt to climb his third eight-thousander.