Canon's Serenar rangefinder tele — 100mm f/3.5 in Leica Thread Mount, manual focus.
The Canon Serenar 100mm f/3.5 is a telephoto rangefinder lens made in Japan for the 39mm Leica screw thread. It carries Canon's Serenar branding from the early 1950s and offered a slightly faster alternative to the earlier 100mm f/4. It served Leica-thread and Canon rangefinder bodies as a compact medium telephoto.
This is a manual-focus, rangefinder-coupled Leica Thread Mount lens with a 100mm focal length and a maximum aperture of f/3.5. The mount is the 39mm Leica screw thread (LTM / L39 / M39). Focus and aperture are set on the barrel by hand. Element count, weight and filter thread are not restated here because they are not verified from the gap data.
A 100mm at f/3.5 gives reach for tighter portraits and distant subjects with compressed perspective, while staying reasonably compact. The moderate aperture keeps it best suited to good light, and it tends to sharpen across the frame when stopped down a little. It works for travel, portraits and general longer-lens photography.
On the used market, inspect for haze, fungus and balsam separation in the cemented groups. Check the coatings for cleaning marks and wear, look for oily aperture blades, and confirm the focus helicoid is smooth. Rangefinder-coupling accuracy matters at 100mm, so test it on a body. It adapts well to Leica M via M39-to-M and to mirrorless using M39-to-E, M39-to-Z or M39-to-RF adapters.