The Canon Serenar 135 mm f/ 3.5 I is a portrait prime lens for 35 mm rangefinder cameras with the M39 screw mount.
The junction plane of the lens with a rangefinder camera has the form of a flange, and not an end ring. Care should be taken when mounting the lens on Soviet cameras so as not to jam or damage a rangefinder's cam. Out of Soviet cameras the lens can be mounted on Zarya viewfinder cameras only (simplified FED-2 without rangefinder) and be used by means of a separate attachable rangefinder. However, it is not very convenient especially if the scale is calibrated in feet. (contributed by pentaxist_B)
Links to online resources:
Posted by: vipzonestudio Date of publication: 10.02.2013