Klein achieved recognition on the photography scene with the publication of New York, a photographic journal of his impressions there in the mid 1950s. The book won the Prix Nadar and provoked intense reaction, both pro and con (1956). He spent the next ten years under contract to Vogue, establishing a reputation as a revolutionary and talented fashion lensman. 
- From 1965 to the early 80s, he abandoned photography and primarily concentrated on film, making various documentaries: 'Broadway by light' (1958), 'Who are you Polly Maggoo?' (1966), 'Mr. Freedom' (anti-American satire), 'Muhammad Ali the greatest', 'The little Richard story' (1979), 'The Essiah' (1999). 
Currently Klein is working on the subject of Paris (his adopted home town), illustrating his personal vision of the city.
At the 48th Thessaloniki Film Festival, the Director Mrs. Despina Mouzaki said that Klein uses his lens to capture the soul of things. "Through his pictures, one can see inside and behind them, not just look at them”.