Olympus OM-10 Quartz viewfinder distorted

pdeeh · May 14, 2017

A few weeks ago I found a little charity shop gem in the shape of an OM10 quartz with 50/1.4.

Seems to generally work fine, no leaks etc ...except the viewfinder is oddly distorting.
It's like looking through a very cheap lens - sharp in the centre and increasingly soft and barrely out to the edges.

Plus, there is a *double* image of the ring round the central microprism.

I can't believe this is typical, and it's not the lens (which works perfectly on my om1n).
Puting my 24 or 135 on the om10 shows the same distortion.

Mirror seems to sit on its bottom stops correctly, though of course I'm certainly no technician.

Pictures seem OK too, though my sort of snaps tend not to show up small focus errors.

My guess fwiw is that some DIY enthusiast has had the focus screen out and put it back in upside down. (as far as I am aware, the om10 did not feature a user-changeable focus screen)

If I run blunt point over the screen from the mirror box, it's zzzzy like a Fresnel.

I only bought it as a bargain backup, and it remains usable save that I feel I bit seasick looking through it, so not the end of the world.

Any thoughts from the clever dudes who do actually know how these things are supposed to be assembled?

BAC1967 · May 14, 2017

Could the mirror not be returning all the way to its correct position?

pdeeh · May 14, 2017

pdeeh said:
Mirror seems to sit on its bottom stops correctly, though of course I'm certainly no technician.

zanxion72 · May 14, 2017

Don't run anything through the fresnel (matte) screen. You'll damage it.
This is how the OM10's finder is like. It feels like vignetting and it is not sharp near the edges. It is of the cheap very amateur SLRs of its era.

Michael L. · May 14, 2017

Perhaps the focusing screen was inadvertently installed upside down. According to the repair handbook (see http://members.chello.nl/pkagei/OM10/OLYMPUS/OM10servman4.htm), the screen should be positioned matte (dull) face up, i.e. towards the pentaprism, and shiny face down.

MattKing · May 14, 2017

zanxion72 said:
This is how the OM10's finder is like. It feels like vignetting and it is not sharp near the edges. It is of the cheap very amateur SLRs of its era.

I don't think so...
I haven't used an OM10 for decades, but I used to work selling them, along with a bunch of other cameras - Canon, Konica, Olympus.
Their viewfinder wasn't as bright or large as an OM1 or OM2, but it was certainly eminently usable, and I sold enough of them to know that most users were happy with them. I would have noticed if they vignetted or weren't capable of sharp focus at the edges.
It is true that the OM10s haven't aged well.
I do own an OM20/OMG, which is the successor to the OM10 and directed to the same market. Its viewfinder is quite usable - reasonably bright and sharp wherever it needs to be.

klownshed · May 14, 2017

zanxion72 said:
This is how the OM10's finder is like. It feels like vignetting and it is not sharp near the edges. It is of the cheap very amateur SLRs of its era.

The OM-10 may have been the budget model but still had a nice viewfinder. The prisms are similar to those in the single digit OMs and are often used to replace damaged prisms due to he silver coating degrading (the OM-10 prisms didn't have the silver).

I think the focussing screens were similar to the single digit OMs too, just without the tab or the mechanism to easily remove them.

Again they often make donors for the posher OMs -- The OM-40 had a really nice bright focussing screen which is often used in the OM-4 and many a 40 is just a donor for the 4.

pdeeh · May 14, 2017

Michael L. said:
http://members.chello.nl/pkagei/OM10/OLYMPUS/OM10servman4.htm), the screen should be positioned matte (dull, 'zzzzy') face up, i.e. towards the pentaprism, and shiny face down.

good link, thanks.

Slightly surprised that it doesn't have keyways which only permit it to be installed the correct way round, but then again as we know it is a cheapie and every little extra like that adds to tooling & assembly costs.

It doesn't seem to be too much of a hassle to disassemble, I'll put it on the list for a rainy day job.

Michael L. · May 14, 2017

Sorry, pdeeh, I didn't read your OP with sufficient care before posting, so just to make it clear: if the screen surface you can touch from the mirror box feels like a fresnel ('zzzzy'), your screen is probably correctly installed. The matte surface and the fresnel are on opposite faces of the acrylic.

pdeeh · May 14, 2017

OK got it.

Well, all very mysterious then.

Perhaps I'm just used to the fabulousness of my OM1n's vf and the 10's simply pales in comparison?

Still, that double image of the microprism circle remains a bit peculiar.

zanxion72 · May 15, 2017

MattKing said:
I don't think so...
I haven't used an OM10 for decades, but I used to work selling them, along with a bunch of other cameras - Canon, Konica, Olympus.
Their viewfinder wasn't as bright or large as an OM1 or OM2, but it was certainly eminently usable, and I sold enough of them to know that most users were happy with them. I would have noticed if they vignetted or weren't capable of sharp focus at the edges.
It is true that the OM10s haven't aged well.
I do own an OM20/OMG, which is the successor to the OM10 and directed to the same market. Its viewfinder is quite usable - reasonably bright and sharp wherever it needs to be.

I haven't said that they are not usable, just their viewfinders are not of the qualities of the higher spec models (makes sense).
This becomes very evident to ones eye after using a better model such as the OM1. I own two of them, the one having a dead shutter, and both have focusing screens with vignetting and soft corners. It does not bother me at all. I still like it, but I prefer using my OM4-Ti that is equally lightweight, offering much more than the lovely OM10.
I am not saying they are useless, just they were the very budget SLRs of that era and their viewfinder is of proportional quality. I would not bother fiddling with it because if damaged (quite easy) the cost of repair is more than the cost of buying another one.
I have read in the past that the OM40's screen being somewhat brighter than the OM4's and I have killed mine just to realize that things were a lot better with the default screen on my OM4-Ti. Of course it might had been that I am not a pro in servicing these cameras, but that is another story.

Ricardo Miranda · May 15, 2017

If your OM10 has sharp centre but fuzzy edges, I would look at the viewfinder optics at the rear.
One of the elements might had detached or is just out of place.

klownshed · May 16, 2017

If the centre split focus ring is not perfect, I'd guess you have a slightly misaligned mirror.

If your mirror is misaligned, the centre circle in the focussing screen can look strange. The further out it is the dimmer the VF will appear and at a certain point the centre circle will appear almost black.

Alternatively, the screen itself might not be seated correctly. Amateur repairs (the sort I attempt ;-) may result in the screen not being installed correctly.

One last possibility, somebody may have put a different screen in it, one designed for a macro or telephoto which will not work as well with a 50mm.

I say that as I once bought an OM-40 that had a macro screen in it (with a cross in the centre). Somebody presumable nicked the standard screen to fit into an OM-4. Not that the 4 really needed the 40's screen...

Olympus OM-10 Quartz viewfinder distorted

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