Mamiya 7II: Fabricating a Dichroic Frame Finder Window
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
Another Mamiya 7II with broken glass. Usually the viewfinder glass is broken but in this case, the frame finder glass was impacted. Since the frame finder glass is a special material on the 7II and is no longer available, I need to fabricate the glass.
While I often hear of Polarized glass used in the Mamiya 7II frame finder illuminating window, in fact, it is not Polarizing glass but it’s a dichroic glass. What I do is cut the correct size out of a larger dichroic glass and then grind one side to make it a “ground glass”. Otherwise looking through it you would see in the inner workings of the rangefinder bits.
The second photo show me about to start on grinding some glass with 800 grit Silicone Carbide. The fluid has not been added so it’s not so messy yet.
Photo three shows the installed window. Depending on how you look at the window, it will look yellow or blue. In this photo, you can see that is it passing yellow light and reflecting blue light on the front of the camera body.
