Leica LTM / M39 Lenses

Leica Thread Mount / M39 rangefinder standard, 1930s-1950s | 35 mm rangefinder

Leica Thread Mount, often called LTM or M39, is the 39 mm screw mount used by early interchangeable-lens Leica rangefinders and many compatible cameras. Its short register and compact bodies helped make 35 mm still photography practical, portable, and lens-interchangeable at a time when larger formats still dominated serious work.

The mount became a de facto rangefinder standard, with lenses from Leica, Canon, Nikon, Soviet makers, and many others. Compatibility can still be nuanced because rangefinder cam geometry, infinity calibration, and accessory finders matter, but the shared screw thread made the system unusually broad.

LTM designs often emphasize compactness and simple, high-contrast formulas: Tessar derivatives, Sonnars, double-Gauss normals, collapsible standards, and early wide-angle rangefinder lenses. These pages are a useful way to compare pre-M rangefinder optics before Leica moved to a faster bayonet.