The Summarex 85 mm f/1.5 first appeared in the Leitz catalogue in 1943, though it was not sold to the public until after the second world war. The only other time Leitz had offered such high light sensitivity was with the Xenon 50 mm f/1.5 – whose construction, however, had not been developed by Leitz, but adopted from the British company Taylor, Taylor and Hobson. In Germany, the lens was manufactured by Jos. Schneider Optics, who also owned the name 'Xenon'.
The new Summarex 85 mm f/1.5 was constructed as a Double Gauss lens, consisting of seven elements in five groups. At 800 grams, the short tele lens was a real heavyweight which placed considerable strain on the camera bodies of the Leica III series. It was one of the reasons why Leitz began to explore new camera concepts – with the M series as a first indication of things to come.