Adapter guide

M39 lenses on L-mount

Yes, this works. M39 has a 28.8mm flange distance and L-Mount Alliance (Leica, Panasonic, Sigma) has 20mm, so a 8.8mm mechanical adapter with no glass fills the gap and infinity focus is preserved. Focus and aperture stay manual.

M39 flange: 28.8 mm
L-mount flange: 20 mm
Adapter thickness: 8.8 mm
Optical elements: None required

Setting it up

On Panasonic S bodies set Shoot w/o Lens to On and enter the focal length for stabilisation. Leica SL bodies accept adapted lenses without a setting change and Leica sells its own R-Adapter L for Leica R glass.

Manual aperture ring, no diaphragm automation. The ring stops the lens down directly.

M39 lenses and their field of view on L-mount

Effective focal length changes with sensor size. The lens itself does not change; the smaller sensor simply captures a narrower part of the image circle.

M39 lenses adapted to L-mount, with effective focal length by sensor format
Lens	Focal length	Aperture	Full frame	Frames like (APS-C (1.5x))	Years	Used value
KMZ Jupiter-8 50mm f/2	50mm	f/2	50mm	75mm	1950s-1980s	$30 to $120

Frequently asked

Do M39 lenses work on L-mount cameras?

Yes. A plain M39 to L-mount adapter works with no optics. M39 has a 28.8mm register and L-Mount Alliance (Leica, Panasonic, Sigma) has a 20mm register, so the adapter is a 8.8mm tube that puts the lens exactly where a M39 body would. Plain threaded adapter for mirrorless, no rangefinder coupling needed. A helicoid adapter adds close focus below the 1m rangefinder minimum. Do not confuse with the Zenit SLR M39 mount, which uses the same thread at a 45.2mm register.

Do M39 lenses focus to infinity on L-mount?

Yes. Because the adapter restores the native 28.8mm register, infinity focus is preserved and the full focus scale on the lens stays accurate. Adapters machined slightly short let the lens focus past infinity by a small margin, which is harmless; adapters machined long stop short of infinity, so buy from a maker with tight tolerances.

What focal length does a M39 lens become on L-mount?

On full frame L-mount bodies (Leica SL series, Lumix S series, Sigma fp) the focal length is unchanged: a 50mm lens frames as a 50mm. On APS-C (1.5x) L-mount bodies (Leica CL, TL, TL2) a 50mm lens frames like a 75mm lens on full frame; the aperture and depth of field at a given distance do not change.