The Leica 50mm F2 Summicron is heralded as the sharpest lens in the World. The Summicron was devleoped as a variation of the 50mm F2 Summitar in 1951. The optical configuration of the Summicron (7 elements in 6 groups) was similiar to the Summitar (7 elements in 4 groups), however, the Summicron utilized the new Leitz glass formulation incorporating the rare earth element Lanthunum. The early Summitar prototypes of the Summicron were marked with an * after the serial number.
The Summicron is a legend among optics. Approaching the theoretical limits of optical performance, the Summicron has been widely accepted among Professional photographers around the world. The design of this optic was so perfect that the Summicron is still manufactured today, and is still the benchmark to which all other lenses are judged.
The Summicron went into production in 1953, first in a screw mount and later in 1954 as a bayonet mount. There were four types of 50mm Summicron's produced. There is much debate as to which type is best, I am fairly positive that the differences in performance are slight, but the early 7 element Summicron has long been a favorite and thought among Professionals and Collectors alike to be the sharpest of the formulations. The later models had a slight increase in contrast over the Type 1. The Type 1 being ideal for Black & White and definately worth having in your camera bag. The build quality of the early units also seem more Robust in the authors opinion.
The early Summicrons came in both Collapsible and Rigid mounts. The collapsible models are great for travel, because they retract inconspicuously into the camera body leaving a small profile that is easy to carry. A specific Dual-Range model was produced with 'eyes' that attached to the lens allowing superior close range ability starting at 1 Meter, 51 or 48cm depending on the production period. This is a fabulous lens, even by today standards.