Carl Zeiss 21mm f2.8 Biogon T* ZM - Lens

Leica’s M mount was introduced in 1953 alongside its first camera, the M3. Despite the rise of the SLR, Leica cameras have continued to succeed as their unique combination of build quality, speed, and discretion sets them apart from competition. The M bayonet mount, and the cameras introduced alongside it, offered (& continue to offer) a number of advantages over SLRs and other rangefinder cameras.

One big advantage is automatic framelines, which react to the lens on the camera to show accurate framelines in the viewfinder. This is even possible with older Leica Thread Mount (LTM) lenses if the correct adapter is used.

Other manufacturers, such as Cosina Voigtländer, Carl Zeiss, Konica, and Minolta, have also produced rangefinder cameras using Leica M mount.