Mamiya C3: Replacing and Calibrating a Broken Focus Screen
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This Mamiya C3 came into the shop with a fairly common issue- a broken focus screen glass. Replacement is straightforward, but the finder needs to be checked for adjustment so that it will focus the same as the taking lens. And, there are shims on the front and rear of the finder focus screen for adjustment. But, before any adjustments can be made, the lens needs to be checked to make sure that the viewing and taking lenses are focusing at the same point. Photo three shows this particular lens being checked.
After I am sure that both lenses are focusing at the same point, I set the camera up in front of a collimator and squirt an infinity target at the camera (photo four). I can then calibrate the viewfinder focus screen as seen in photo five.
