Mamiya 7 Lenses: Evaluation Process and Testing Steps
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
These Mamiya 7 lenses were sent in for evaluation and here is the process that I do with these lenses:
1.) external observation for impact damage or other trauma
2.) check focus on autocollimator
3.) test shutter speeds
4.) test output of diaphragm information that is sent to camera body
5.) test of rangefinder cam movement
The shutters are usually in good shape. What I do often see is broken flex cables used to send out the diaphragm information to the camera and also rangefinder cams that are not adjusted correctly.
The first video clip shows a 50mm lens that has correct rangefinder cam movement. The second clip shows a 43mm lens that has a 0.02mm error. While you might not notice this on a 43mm lens at a distance, close ups and wide open shooting really need very close rangefinder calibration to get the optimum sharpness of the lens.
The final video clip shows the technique that I use to test diaphragm output information. I measure the output of the lens and make sure that the diaphragm resistance (in this case 1.8K-6.6K) flows smoothly at all f stops. A broken cable is quickly seen as an open in the circuit.
