Adapter guide
Pentax K lenses on L-mount
Yes, this works. Pentax K has a 45.46mm flange distance and L-Mount Alliance (Leica, Panasonic, Sigma) has 20mm, so a 25.46mm mechanical adapter with no glass fills the gap and infinity focus is preserved. Focus and aperture stay manual.
- Pentax K flange
- 45.46 mm
- L-mount flange
- 20 mm
- Adapter thickness
- 25.46 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.
Automatic diaphragm. Pentax-A and later lenses add an A position on the ring that hands aperture control to the body; leave it off A on an adapter.
Pentax K 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.
| Lens | Focal length | Aperture | Full frame | Frames like (APS-C (1.5x)) | Years | Used value |
|---|---|---|---|---|---|---|
| Pentax SMC Pentax 50mm f/1.2 | 50mm | f/1.2 | 50mm | 75mm | 1975-1990s | $300 to $800 |
| Pentax SMC Pentax-M 50mm f/1.4 | 50mm | f/1.4 | 50mm | 75mm | 1977-1984 | $60 to $210 |
Frequently asked
Do Pentax K lenses work on L-mount cameras?
Yes. A plain Pentax K to L-mount adapter works with no optics. Pentax K has a 45.46mm register and L-Mount Alliance (Leica, Panasonic, Sigma) has a 20mm register, so the adapter is a 25.46mm tube that puts the lens exactly where a Pentax K body would. Plain adapter ring. Because K keeps the 45.46mm M42 register, M42 lenses also mount on K bodies with a thin adapter and keep infinity.
Do Pentax K lenses focus to infinity on L-mount?
Yes. Because the adapter restores the native 45.46mm 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 Pentax K 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.
More on this mount: Pentax K mount reference