Produced in very small quantities, (and not only rested on drawing papers) the GOI CV-catadioptric lens 20mm f/0,5 (YES, zero point five) stands as the fastest lens ever built, Two full stops wider than the actual top-scorers (the Noctilux-M and Canon EF-L, both "limited" at f/1,0); this amazingly, bulky 9,7kg of lens (with a mere 20mm focal length...) was born on spring 1948, and it should have been a really specialized guy, as it could match just a mere 2,9mm image circle; This monster puts again in sharp focus how much the old Soviet lens technology have reached... courtesy Mario Cavina.