Canon's wide rangefinder screw-mount prime — 25mm f/3.5 in Leica Thread Mount, manual focus.
The Canon 25mm f/3.5 is a wide-angle rangefinder lens made in Japan for the 39mm Leica screw thread. It comes from Canon's rangefinder era, when the company built a broad line of screw-mount optics for its own bodies and for Leica-thread cameras. As a wide 25mm it sat at the short end of Canon's rangefinder range and typically shipped alongside an accessory optical viewfinder, since most rangefinder bodies did not show a 25mm frame in the finder.
This is a manual-focus, rangefinder-coupled Leica Thread Mount lens with a focal length of 25mm and a maximum aperture of f/3.5. The mount is the 39mm Leica screw thread (LTM / L39 / M39). Focus and aperture are set by hand on the barrel. Other optical details such as element count, weight and filter thread vary by production run and are not restated here to avoid guessing.
At 25mm the lens gives a wide field suited to interiors, architecture, tight streets and landscape work. Stopped down it holds a deep zone of focus useful for grab shots where precise focusing is awkward. Wide-angle rangefinder optics of this period tend to show some falloff toward the corners at full aperture, which eases as you stop down.
On the used market, inspect for haze inside the elements, fungus, and balsam separation between cemented groups. Check the coatings for cleaning marks and wear, look for oily aperture blades, and confirm the focus helicoid turns smoothly. Verify rangefinder-coupling accuracy against a body before buying. These lenses adapt well to Leica M via an M39-to-M adapter and to mirrorless bodies using M39-to-E, M39-to-Z or M39-to-RF adapters.