Leica's first Summicron — the collapsible 50mm f/2, coated screw-mount standard lens.
The collapsible Summicron 50mm f/2 was the first Summicron, launched in the early 1950s as the successor to the Summitar and the new benchmark standard lens for the Leica system. In screw mount it brought Leitz's post-war optical work to the 39mm Leica Thread Mount in a compact collapsible barrel.
This is a manual-focus, rangefinder-coupled Leica Thread Mount lens with a 50mm focal length and a maximum aperture of f/2, built with a collapsible barrel that retracts into the body. It is a coated design in chrome over brass. Verify the filter size and any thorium-glass considerations on a given example rather than assuming.
A 50mm f/2 is the classic rangefinder standard for street, travel, general and portrait work, and this first Summicron established the rendering that later versions refined. It is sharp stopped down while keeping a smooth, moderate-contrast character wide open that many photographers still seek out.
This is desirable collector glass and values are driven by condition and originality. Some early Summicron elements used thorium glass that can yellow over time, which is worth checking; also inspect for haze, cleaning marks, coating wear and element separation, confirm the collapsible mount locks firmly, and check focus feel and dry aperture blades. It adapts to Leica M via a 39-to-M adapter and to mirrorless with an L39 adapter.