Mamiya 7: Rangefinder Control Mechanism Explained
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
The first photo shows most of the major parts of the Mamiya 7 : the main body, wind mechanism, rangefinder, shutter speed assembly and front lens mount assembly. While I have the camera at this level of disassembly I thought it might be a good time to show some of the parts of the rangefinder control mechanism.
I do a lot of rangefinder work on the Mamiya 6/7 and while each lens has a rangefinder cam that can get out of adjustment, the majority of calibrations are on the body, not the lens. These videos will show why.
In the first video, the rear of the lens rangefinder cam is show sliding over the lens mount rangefinder contact roller. This is the first stage
The second video shows the next stage where the lens mount contact roller moves the body transfer levers.
Next, the rangefinder is shown from the rear with its movement.
So, there are a number of parts here that can get out of calibration especially with any sort of impact to the camera.
By comparison, the final video shows the rangefinder cam in a 65mm lens and this is the only moving part in the lens rangefinder system (other than the helicoid of course). Generally, when a lens comes into the shop with a rangefinder cam out of spec, it is because the lens has been disassembled and not calibrated.
