Mamiya 6 75mm Lens: Unsharp Images from Loose Front Element
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
Sometimes the problem on a camera/lens turns out to be something different than what is first expected. In this case, my client told me that his Mamiya 6 75mm lens has a rangefinder issue. And, that it had been recently serviced for fungus removal. So, while it is not really common for these particular lenses to be out of calibration in the rangefinder department, the fact that it had been serviced might be a clue that something was not reassembled correctly.
When the lens first arrived, I checked the rangefinder cam as seen in the first photo. It was out by -0.045 and while this is out of specs by a bit (specs are -0.015 to 0.00), it should not be the cause of unsharp photos.
On putting the lens on the collimator I noticed a very not sharp image as shown in photo three. The fourth photo shows something suspicious- the filter threads are very shallow. But the name ring was on tightly. So, after removing the name ring I saw that the front element group was barely screwed in and was preventing the name ring from attaching very deeply and of course the rear and front element spacing was far off causing a focus problem.
After tightening everything up and calibrating the rangefinder it was good to go. The final photo shows the image after the service.
