Leica 50mm Collapsible Elmar 50mm F2.8 Elmar Collapsed into M4 Body/50mm Summicron shown for Comparison This is a Great lens, the lens that started it all.  Fabulously Sharp and Wonderfully Contrasty, and in a package that collapses inconspicuously into the body of the camera.  The lens you take with you when you don't want to take a lens with you! This lens has been much overlooked since the introduction of the Summicron in 1953.  It is one of my favorite lenses in the Leica system.  Fast enough for most situations, Superb Quality and Resolution and a profile so dimunitive that you do not even know you have a lens with you.  This lens gets carried around with me more than any other Leica lens.  Do not limit yourself to just the Summicron, the 50mm Elmar can be had at attractively low prices these days and is worth your time & money investigating. The Elmar was first introduced as a screw mount lens as a replacement for the Elmax back in 1925.  The Elmar was made in M mount in 1954 as an F3.5 coated model.  Later becoming a faster F2.8 in 1957 thanks in part to the new Leica optical glass formulation utilizing the rare earth element, Lanthunum.  A second version of the F2.8 model was introduced in 1995 with new Coatings and a different glass formulation but no infinity lock.  (Personally I find the infinity lock on older Leica lenses of much use and easy to operate.) Specifications Elmar M 50mm F3.5 1954-1961  SN 1,124,000-1,913,000 Finish Chrome Mount Collapsible Lens Elements 4 in 3 Groups Filter Size 39mm Apertures F3.5-F22 Angle of View 45 Degrees Minimum Focus Distance 1 Meter Units Produced 13,198 Weight 210 Grams 50mm F3.5 Elmar Elmar M 50mm F2.8 1957-1974  SN 1,350,000-2,700,000 Finish Chrome Mount Collapsible Lens Elements 4 in 3 Groups Filter Size 39mm Apertures F2.8-F22 Angle of View 45 Degrees Minimum Focus Distance 1 Meter Units Produced 50,000 Weight 220 Grams 50mm F2.8 Elmar First Version Elmar M 50mm F2.8 Second Version 1995-Current  SN 2,700,000-Current Finish Chrome Mount Collapsible Lens Elements 4 in 3 Groups Filter Size 39mm Apertures F2.8-F22 Angle of View 45 Degrees Minimum Focus Distance 70 cm Units Produced N/A Weight 200 Grams