Adapter guide
M39 lenses on Canon RF
Yes, this works. M39 has a 28.8mm flange distance and Canon RF mount 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
- Canon RF flange
- 20 mm
- Adapter thickness
- 8.8 mm
- Optical elements
- None required
Setting it up
Enable Release shutter w/o lens and turn on MF peaking. Canon APS-C bodies use a 1.6x crop rather than the 1.5x of other systems.
Manual aperture ring, no diaphragm automation. The ring stops the lens down directly.
M39 lenses and their field of view on Canon RF
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 (1.6x)) | Years | Used value |
|---|---|---|---|---|---|---|
| KMZ Jupiter-8 50mm f/2 | 50mm | f/2 | 50mm | 80mm | 1950s-1980s | $30 to $120 |
Frequently asked
Do M39 lenses work on Canon RF cameras?
Yes. A plain M39 to Canon RF adapter works with no optics. M39 has a 28.8mm register and Canon RF mount 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 Canon RF?
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 Canon RF?
On full frame Canon RF bodies (EOS R, RP, R3, R5, R6, R8) the focal length is unchanged: a 50mm lens frames as a 50mm. On APS-C (1.6x) Canon RF bodies (EOS R7, R10, R50, R100) a 50mm lens frames like a 80mm lens on full frame; the aperture and depth of field at a given distance do not change.
More on this mount: M39 mount reference