Summicron 50mm f/2 collapsible

When Leitz introduced the name "Summicron" in 1953 they were signalling a new optical benchmark: an f/2 maximum aperture (the "cron" suffix) with correction levels that justified the premium price. The collapsible version used a screw thread to retract the lens barrel into the body, keeping the whole package small enough to fit in a coat pocket — a deliberate nod to the collapsible Elmar tradition.

For beginners: the collapsible Summicron is the grandfather of the 50mm Summicron lineage that Leica still sells today. It was made for both the screw-mount and early M bodies; the M-mount version must never be collapsed on a digital M body as the rear element will strike the sensor. On film bodies it remains a fully practical shooter — the optics are sharp in the centre, the rendering is slightly warmer and softer at the edges than later rigid versions, and the history attached to each copy is tangible.