Leica Summicron 50mm f2 R and M / US 4,123,144

Designed by Walter Mandler - it seems these lenses are the best one can obtain using the traditional 6 element double gauss design with only spherical surfaces.

• Double Gauss lens design: a review of some classics using modern methods
• Design Of Basic Double Gauss Lenses, Walter Mandler, 1980
• PhotonsToPhotos Optical Bench - 50mm Summicron R
• Zemax file 50mm f2 Summicron R
• PhotonsToPhotos Optical Bench - 50mm Summicron M
• Zemax file 50mm f2 Summicron-M
• Marco Cavina Article