How to take care of the Contax II/III viewfinder ?

[Wolkengrau]

Hello,

My Contax III is in complete operable condition and I really want to take care of it. Though, the viewfinder piece of glass (a prism part of the rangefinder I suppose) is bordered with yellow, golden traces, like shattered glass. I do not really know what that is nor what causes it to appear, but if anyone has informations about it I am glad to read them. I have seen the same traces on many other Contax viewfinders.

In hope to make my Contax last, any other tips that you have to avoid mistakes and improper use are also very welcome.
Thanks 🙂

 

[Coldkennels]

Assuming that the Contax III is built the same way as the Kievs that followed it, the good news is that the thing you're looking at is unlikely to be a failing prism.

The whole rangefinder/viewfinder arrangement in these things is pretty "simple": there's two pieces of cover glass on the front (one per window), two prisms at the RF end that are glued in place, two more pieces of glass housed together to act as a diopter at the back of the viewfinder, and one long prism to carry the RF image to the VF. That means that, short of actually cracking one of those glass components, you're unlikely to have a total failure of a Contax rangefinder due to Balsam separation like you find in early Ms.

However, the bad news is that the real weakness of the Contax (as far as I'm concerned) is the fact the glue for those two prisms at the RF end does fail. It ages, dries out, and with a bit of hard shock to the camera, can allow one of the prisms to move out of alignment - and there's very little adjustment that can be done without removing the prism and repositioning it. And that aging glue? it looks yellow/gold, so I'm betting that's what you're seeing.

(I say all this because I've just strip-cleaned a lot of fungus out of a Kiev and found this exact problem! I'm now going to have to go through the hassle of figuring out a suitable glue AND how to reposition everything for accurate rangefinder calibration. Urgh.)

If I'm right, the best thing you can do is not subject the Contax to hard shocks (i.e. don't drop it). If the RF is currently calibrated correctly, you could add extra glue to where the prisms meet the frames that hold them as a preventative measure, but I do not recommend anyone opens a Contax or Kiev unless they know what they're doing. They're absolute nightmares internally.

 

[Mr_Flibble]

Sounds like prism separation / balsam deterioration to me.