Lens adapter compatibility

M42 screw mount lenses on Canon RF cameras

Can you use M42 screw mount lenses on Canon RF cameras? Yes, with a simple mechanical adapter (manual focus). The M42 screw mount flange distance is 45.46 mm and Canon RF is 20.00 mm, a difference of +25.46 mm.

+25.46 mm

Space for the adapter

45.46 mm

M42 screw mount flange

20.00 mm

Canon RF flange

Verdict: Yes — a simple 25.5 mm adapter keeps infinity focus.

What to expect#

Aperture control: these are mechanical lenses with aperture rings — set the aperture on the lens and shoot in aperture-priority or manual.

Focus: use focus peaking and magnification in the viewfinder. Exposure metering works normally because the camera meters through the lens at working aperture.

M42 screw mount lenses you could adapt#

Canon RF cameras#

Other systems for M42 screw mount lenses#

Sony E-mount Nikon Z Fujifilm X-mount Micro Four Thirds L-Mount Canon EF-M Fujifilm G-mount Hasselblad XCD Nikon 1 (CX)Pentax Q

Frequently asked questions#

Will M42 screw mount lenses autofocus on Canon RF?

No — adapted lenses are manual focus on this combination.

Does a M42 screw mount to Canon RF adapter affect image quality?

A glass-free adapter is just a precisely machined spacer, so image quality is unchanged when it is built to the right thickness. Cheap adapters can be slightly too thin or thick, which shifts the infinity mark.

Last updated October 03, 2026 · How we calculate · Sources