Leica M39
A threaded lens mount standard used on Leica rangefinder cameras, also known as Leica Screw Mount or LTM.
Overview
The Leica M39 is not a standalone camera model but a screw-thread lens mount system used by Leica on rangefinder cameras from approximately 1923 to 1965. Also referred to as Leica Screw Mount (LSM), Leica Thread Mount (LTM), or L39, this mount was integral to early Leica camera design. It was specifically engineered for rangefinder lenses, ensuring proper alignment and focusing functionality. Leica offered factory upgrades during this period, allowing owners to modernize earlier models while retaining original serial numbers. Cameras assembled at the Midland facility (Ernst Leitz Canada) were rarely engraved with "Midland."
Specifications
| Flange focal distance | 28.8 mm |
| Product type | camera lens mount |
Design
The Leica M39 is a screw-thread lens mount designed specifically for rangefinder lenses, not SLR systems. This mount is mechanically distinct from Soviet M39 mounts, which use a 25.4 TPI thread and are incompatible despite superficial similarity.
Context
Lenses designed for SLR systems, such as the Mir-1B, cannot achieve proper focus when adapted to the Leica M39 mount due to optical and mechanical mismatch. The Leica M39 standard is not interchangeable with Soviet M39-threaded cameras like the Zenit or Chaika, which differ in thread pitch and flange distance. Adapters to other systems, such as the M bayonet, may disrupt rangefinder coupling, affecting focusing accuracy.
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