Strange item inside OM2N viewfinder?

geostog · May 23, 2014

After a really disappointing experience purchasing an OM2n, I challenged my luck again and bought for a third time a body.
I have to say that this one seems to be fine. There are very few slight marks of use and generally gives the impression that it is barely used. The only thing that gives away its age is the foam. The light seals are seriously deteriorated and will definitely need to be replaced.
But my mind is in the viewfinder. Looking through the viewfinder, I get to see something strange on the bottom. To me it looks like the top of a prism, I say that because of my experience disassembling some cameras. That item, does not block the view, does not move and generally it does nothing that worrying me.
Should that be there? I don't remember seeing something like that on the previous bodies I had and that is the reason I ask for your help. What is that, should I worry about it, should I return the camera and get my money back?

film_man · May 23, 2014

I'm not 100% sure and I no longer have an OM-1 but there is foam in the prism too which will deteriorate over the years so it could be that it is that? I remember my repair guy saying that if you don't take care of it the foam deteriorates to some gas or whatever that will damage the prism or something along those lines...

geostog · May 23, 2014

I tried to take some photos of what I see. They both came out rotated but you will get the point.
The first one is straight from the viewfinder. The object I am telling you is right bellow the light and it looks like a pyramid.
The second one is from the lens mount, after I've removed the focusing screen. You can see it as a pyramid I the center of the image, inside the prism.

pdeeh · May 23, 2014

that's right.
there's a thread about it here (there was a url link here which no longer exists)

AgX · May 23, 2014

I cannot make much out of your photographs. But with one Zenith-E of mine I see a straight, somewhat rough line in the finder. I assume it to be the central edge of the rooftop prism having corroded reflective coating

geostog · May 23, 2014

Thank you for your replies.
I though it could be the foam. The fix seems to be quite complicated. My main concern is that if this fix is essential for the camera's function. Can it live without it?

MattKing · May 23, 2014

Without removing the deteriorated foam, it will continue to get worse, and will damage the prism.

The camera will work fine (mostly) but the viewing and manual metering will be impacted.

wblynch · May 23, 2014

The prism 'corrosion' is well known in OM1 and some OM2 cameras. It comes from deteriorated foam light seals. Removal of all the internal foam around the prism is required and if the corrosion is too bad, a replacement prism should be fitted.

If a replacement prism is not easily found, the corrosion can be cleaned to good effect and the original prism replaced. A small discoloration would be seen in the viewfinder but never affect the photos taken.

Or you could just ignore it all together.

Ap507b · May 23, 2014

Does anyone know please whether the OM2 Spot Program is susceptible to this as well?

I haven't been able to find any mention on Google but the one that I bought last year from ebay has a small narrow vertical smudge mark at the bottom centre of the viewfinder. It isn't on the focusing screen & I am wondering if it could be the foam?

Thanks.

Peltigera · May 24, 2014

If it looks like the top of a prism, could it be a reflection of the pentaprism reflected on the top of the focusing screen?

thuggins · May 28, 2014

geostog said:
I though it could be the foam. The fix seems to be quite complicated. My main concern is that if this fix is essential for the camera's function. Can it live without it?

The fix is very simple. You just remove the top cover and clean away all the nasty black gunk that the foam has evolved into over the years. The instructions for removing the cover are available on the web. Once the gunk is cleaned up you can replace the prism with a new one, but of course you have to find a new one that isn't damaged. An easier solution is to feather the edges of the damaged coating using Simichrome, toothpaste or similar. Once the hard edge is gone the damage will be essentially invisible thru the viewfinder.

I have use both the replace and repair methods on various OM's thru the years. The repair method works fine and is cheaper unless you happen to have a trashed OM to cannibalize.

mgb74 · May 28, 2014

IIRC, the prisms of some low end (and cheap) Olympus SLRs can be used.

frank · May 28, 2014

mgb74 said:
IIRC, the prisms of some low end (and cheap) Olympus SLRs can be used.

I've read about this too.

geostog · May 29, 2014

Thank you all for your replies!
I've seen some videos on how to clean the prism and seems like something I can do. I ordered a lens spanner so I can remove the top plate.
I will try cleaning and polishing the prism just like thuggins suggested and see if everything is ok.
I've read that an OM-10 prism can be used. Is that correct? Owing an OM-10 and comparing to an OM-2, the viewfinder on the OM-2 seems much bigger, does that have to do with the prism or it is irrelevant?

Strange item inside OM2N viewfinder?

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