Gustav Kleinberg

" . . . Leica always had the obtainment of the best possible optical glasses for its M lenses as one aim of paramount importance, and the examples are manifold: the thorium oxide glass nD= 1,69112 vD= 54, 8 included in four of the lenses of the optical formula of the Leitz Summitar* Summicron (I) f= 5 cm 1:2 Original Project 1950 designed by Gustav Kleinberg and Otto Zimmermann (which also had a flint lead-glass plate to avoid film fogging by radiation) . . ." Source - José Manuel Serrano Esparza

E. Leitz Photographic Patents by Gustav Kleinberg

• 1950 JUL 20 - PHOTOGRAPHIC OBJECTIVE LENS SYSTEM (8 / 6) with Otto Zimermann see Summicron (I) f= 5 cm 1:2
• 1958 AUG 21 - PHOTOGRAPHIC OBJECTIVE (7 / 5) with Otto Zimmermann and Eugen Hermanni
• 1961 APR 11 - PHOTOGRAPHIC OBJECTIVE (9 / 7 - 8 / 6) with Heinz Marquardt, Otto Zimmermann and Eugen Hermanni