 Despite having no formal training as a photographer, Klein won the Prix Nadar in 1957 for "New York", a book of photographs taken during a brief return to his hometown in 1954.Klein's work was considered revolutionary for its "ambivalent and ironic approach to the world of fashion", its "uncompromising rejection of the then prevailing rules of photography" and for his extensive use of wide-angle and telephoto lenses, natural lighting and motion blur.The New York Times' Katherine Knorr writes that, along with Robert Frank, Klein is considered "among the fathers of street photography, one of those mixed compliments that classifies a man who is hard to classify."