Olympus OM-10 metering problem

David Lyga · Mar 29, 2019

I have two OM-10 models and each gives proper exposure on 'auto'. The problem with BOTH is that the red shutter speed indicator light in the VF shows erroneous speeds. For example, if the speed the red light shows is, say, 1/60, the shutter might be more like 1/4 or 1/8. Again the ACTUAL, TIMED shutter speed CHOSEN FOR ACTUAL EXPOSURE is correct for the proper exposure, but the shutter speed INDICATED in the VF is way off.

My question is this: How can there be a disconnect between the indication and the actual speed? Of course, I am not talking about a 'manual adapter' situation, but wholly, the auto exposure. This is as interesting as it is frustrating, as I have never had a disconnect between indication and actual on any camera.

I know that this camera weighs light even DURING exposure, but the scene is, in all attempted cases, static, as far as light is concerned. - David Lyga

MattKing · Mar 29, 2019

The OM-10 meters off the shutter curtains/film. There is a separate metering system designed to provide information in the finder, but that system doesn't control the actual exposure, unless you are using it to meter manually - in which case it is controlling you, and you are controlling exposure .
That secondary system isn't working properly in your cameras.
Any chance your lens aperture is sticking, leading to a dimmer viewfinder and inaccurate indications in the viewfinder? The 50mm f/1.8 lenses seem prone to sticky apertures.

David Lyga · Mar 30, 2019

MattKing said:
The OM-10 meters off the shutter curtains/film. There is a separate metering system designed to provide information in the finder, but that system doesn't control the actual exposure, unless you are using it to meter manually - in which case it is controlling you, and you are controlling exposure .
That secondary system isn't working properly in your cameras.
Any chance your lens aperture is sticking, leading to a dimmer viewfinder and inaccurate indications in the viewfinder? The 50mm f/1.8 lenses seem prone to sticky apertures.

Thank you Matt. I was not aware that there were two separate metering systems. (I already knew about the sensor reading the film plane.) I don't know if I like that 'advancement' because it is prone to deception. - David Lyga

MattKing · Mar 30, 2019

David Lyga said:
Thank you Matt. I was not aware that there were two separate metering systems. (I already knew about the sensor reading the film plane.) I don't know if I like that 'advancement' because it is prone to deception. - David Lyga

The good news is it gives an indication if your aperture needs cleaning - something that isn't always obvious.

M-88 · Mar 31, 2019

I'm too little too late to this party, but I think it's worth mentioning that what MattKing said is applicable to OM-2, OM-20 and OM-4 as well, even though OM-2 (first of the bunch that offered OTF metering) has two metering cells on either sides of mirror box while others have just one in the center. And one of OM-2's metering circuits can't be turned off with on/off switch - the camera exposed properly even when turned off, at speeds above 1/60

BMbikerider · Mar 31, 2019

Bearing in mind that the OM10 models can be well over 40 years old this may be a sign of photographic Altzymer's setting in. In other words - something is broken. I doubt if there are any spares available apart from cannibalising other similar models.

If you have a manual adapter for your camera does this make it work correctly?

David Lyga · Mar 31, 2019

BMbikerider said:
Bearing in mind that the OM10 models can be well over 40 years old this may be a sign of photographic Altzymer's setting in. In other words - something is broken. I doubt if there are any spares available apart from cannibalising other similar models.

If you have a manual adapter for your camera does this make it work correctly?

The manual adapter works well.

Bill Burk · Mar 31, 2019

Also.... do you have film in the camera or are you firing dry? You get a way different exposure when the camera reads “off the pressure plate”.

It looks like not very much light, since the plate is black, so you get longer shutter open time without film loaded.

MattKing · Mar 31, 2019

Bill Burk said:
Also.... do you have film in the camera or are you firing dry? You get a way different exposure when the camera reads “off the pressure plate”.

It looks like not very much light, since the plate is black, so you get longer shutter open time without film loaded.

Bill,
I think what you are describing is what you observe about the shutter, while David's problem is with the reading in the finder.
By the way, if the finder reading is off, don't use it to set the camera with the manual adapter.

David Lyga · Apr 2, 2019

Bill Burk said:
Also.... do you have film in the camera or are you firing dry? You get a way different exposure when the camera reads “off the pressure plate”.

It looks like not very much light, since the plate is black, so you get longer shutter open time without film loaded.

I think that that is a moot point, Bill, as there is not a 'consistency' between the two meters: the one that reads off the film plane and the one that reads off the mirror. But your point is well taken. - David Lyga

David Lyga · Apr 2, 2019

MattKing said:
Bill,
I think what you are describing is what you observe about the shutter, while David's problem is with the reading in the finder.
By the way, if the finder reading is off, don't use it to set the camera with the manual adapter.

Yes, I already have come to the sorry conclusion that the 'meter for reading information' is no good. This forces me to come to the (again) sorry conclusion that this duplex metering, although good idea theoretically, was not such a good idea in practice. This is most likely why other manufacturers did not adopt this 'advancement'.

I am going to perhaps anger some who love Olympus (although I love their rangefinders). I find no comparison between the build quality of Olympus SLRs (including the OM-1 and OM-2) with either MInolta (mechanical or electronic), or Pentax (mechanical). I consistently find the Olympus SLRs to be too delicate, lacking the robust build quality of the others. However, I find the electronic Pentax ME and ME Super to be of similar 'delicate' build quality. I say this after years of dissecting these popular cameras. - David Lyga

MattKing · Apr 2, 2019

It could be something as simple as some unwanted debris on the surface of the sensor that provides the reading for the finder.

Olympus OM-10 metering problem

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