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OM-1 viewfinder oddity

Nat Pelson , Aug 29, 2010; 12:23 a.m.

I just got a black OM-1 [MD] off of Ebay and it seems to be in perfect shape except for one thing.
When looking through the viewfinder, you can see a pair of "somethings" at the bottom of the screen. Some of it intrudes up into the image area and some of it extends down below the image. I took out the focus screen and very gently probed with a clean q-tip. They are up in the pentaprism somewhere apparently near the top apex. The objects are similar but NOT mirror images and clear like an insect wing. Could it be a clear adhesive from some sort of repair?
It obviously wont affect pictures taken with the camera but it is kinda annoying.
Btw, this is my first experience with an Oly, I'm a Minolta man, but I have to say I'm impressed. I didn't imagine the OMs were THIS small, build quality seems top notch too.


Chris Nielsen , Aug 29, 2010; 03:37 a.m.

Common problem with those cameras, there is stuff stuck to the prism, some black foam stuff, that breaks down over time and turns to goo

Starvy Goodfellows , Aug 29, 2010; 04:57 a.m.

There are odd bits and pieces on my OM4 as well but I have got used to not seeing them when I shoot. I am prone to just wiping the lens just before exposure as it always feels like the bits would be on my shots!

david carroll , Aug 29, 2010; 11:47 p.m.

Early OMs had a piece of black foam across the top of the pentaprism - some sort of light shielding that ultimately proved to be redundant, as is was absent in later models. Unfortunately, all foam - be it mirror bumpers, rear door seals, or pentaprism foam, turns to crap after 15-20 years. The problems is that the degraded pentaprism foam will eat through the mirroring of the pentaprism, leaving permanent and irreparable blotches in the viewfinder. The only thing is to remove the foam before it chews up your pentaprism. You could do this yourself if you're up to taking the top off your OM, or you could have a professional do it (see www.zuiko.com). Camtech will remove this foam (and convert your OM-1 to use current silver oxide batteries) as part of a standard OM-1 overhaul. Well worth it if you're planning on keeping your OM-1.

Matthew Newton , Aug 30, 2010; 09:24 a.m.

You are going to have to remove the top plate to get at the pentaprism. Then you can clean the foam off of it. However, the couple of OM's I've seen where there are artifacts in the view finder, this generally occurs because the foam has degraded and eaten through the pentaprism mirroring.
Alternately if you really like your sample, you could try getting one or two parts OM-1s and stealing the pentaprism out of them. I've gotten my hands on a couple of non-working OM-1s and stripped parts off them, in one case a pentaprism to get another couple of OM-1s working properly.

John Hermanson , Aug 30, 2010; 10:23 a.m.

Plain OM-1 below approx. serial number 1,110,000 had foam pressing against the prism. The foam turns to goo over 30 years and eats through the coating of the prism. Blotches may be dark green or black.
Best repair is to replace prism with good one. Other option: blotches can be cleaned off, and glass retains most of it's reflectivity without the aluminum coating. Results can be quite acceptable depending on how finicky the user is. John

Nat Pelson , Aug 30, 2010; 12:47 p.m.

Yeah mine is still clear with just a rim. I wonder if it has already been cleaned?
I have yet to run film through it, once a wien cell arrives I will check it out and go from there. I was all over Camtech's site and if the OM-1 is functioning properly I will probobly let him work his voodoo on it. I'm liking this camera more and more as I fiddle with it.

Matthew Newton , Sep 01, 2010; 05:55 p.m.

It certainly grows on you. For batteries just pickup 675 zinc-air batteries at any pharmacy or big box store. I typically get them for about $10 for 6 of them. Each one lasts about 2-3 months.

Michael White , Sep 23, 2010; 10:27 a.m.

I replaced the prism in my OM-2 with the prism from a parts OM-10.
OM-10's can be picked up much cheaper from ebay.
The OM-10 prisms did not have foam applied and as far as I know
its the same exact part.

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