Just bought a M645 the older version. Of course the finder prism has degrading foam damage.
Wish there was more info on apug about this problem. Then I would have known what questions to ask.
My main reason for this thread is has anyone tried to have their prism re-coated?
I know people buy up the un-metered version to get good prisms for their metered ones.
I recently contacted a person that vacuum coats telescope mirrors.
He gave me a quote of $50. A little much in my opinion.
If I knew what happens to all the bad ones maybe we could get a group rate on the coating.
Just wondering.

I tried to open my prism up once to just clean it, and couldn't for the life of me figure how to get this thing open. I gave up. $50 for repair seems much considering an excellent one can be bought for $59 at KEH right now. Obviously not the answer you were hoping for. My cds prism doesn't have any of the foam degradation issues you cite, sorry to hear. I am mostly waist level finder but use the prism time to time and would be less than thrilled if it wasnt working as designed!

Hi zsas
Yes I know the repair really doesn't make sense at that price. A shame turning all those prisms into paper weights though.

I don't know how old your prism is but I was told that there are two kinds of prisms. Ones that have foam damage and those
that will have foam damage.

I guess back then they used what was available. Strange though I have two 35mm SLR's. One minolta and one mamiya.
The mamiya is way newer than the minolta and the mamiya is the one with light seal foam degradation. Go figure !!

I forgot to mention that there are two screws under the front name plate.

Yeah, I have one (unmetered) (in addition to the CDS one) and would love to get it fixed / replaced. =/ Maybe I should just find a parts one to swap. I think I saw repair manuals online for the prisms.