Klein has worked with Frankfurt Opera since 1994, and since 2013 has been Head of Lighting. His lighting designs for the company include Jeanne d’Arc au bûcher and La Damoiselle élue, The Rake’s Progress, The Gambler, Serse, Ezio, Eugene Onegin, Stiffelio, Radamisto, Giulio Cesare in Egitto, Don Carlos, A Life for the Tsar, Euryanthe, The Excursions of Mr Broucek, Otello, Adriana Lecouvreur and Lachenmann’s Das Mädchen mit den Schwefelhölzern. For Barrie Kosky his lighting designs include Carmen, Duke Bluebeard’s Castle and Dido and Aeneas (Frankfurt Opera), The Fiery Angel (Bavarian State Opera and Munich Opera Festival), Saul (Glyndebourne Festival) and Carmen (Royal Opera House, London)

Klein’s other credits include Werther (Liceu, Barcelona) for Willy Decker, La traviata (Graz, Seattle, Theater an der Wien and English National Opera) for Peter Konwitschny, Lucrezia Borgia (Bavarian State Opera) for Christof Loy, Die tote Stadt (Graz), Un ballo in maschera (Bavarian State Opera) and The Cunning Little Vixen (Hamburg) for Johannes Erath, Boris Godunov (Karlsruhe) for David Hermann and Salome (Salzburg Festival, Royal Danish Opera and Norwegian National Opera) for Stefan Herheim. His awards include the Knight of Illumination Award, in 2014 for Duke Bluebeard’s Castle at the Edinburgh Festival and in 2016 for Saul for Glyndebourne Festival, and the 2017 Helpmann Award for Best Lighting Design.