Adjusting OM2 meter

[BetterSense]

I have an OM2n, and the meter is wrong. It says that it's dimmer than it really is, causing me to overexpose. I could adjust the film speed to compensate, but that would be confusing and I would like to fix the meter itself. Is this something that's easy to adjust?

Also, how long should a set of batteries last? I'm only gettting a few months of life out of Energizer silver oxide batteries, and when they go, the camera is useless.

 

[Ulrich Drolshagen]

The OM2n doesn't have just one meter but two. In automatic mode the display in the finder just serves informative purposes. The metering is done realtime during exposure by the second system. May be you should first find out which system is off. If they are both off by the same amount you may have a problem with the shutter instead.
AFAIK the cam is so highly integrated and tiny that repairing it is not an easy task for a layman. You should better get it CLA'd by an repairsman. It is worth it.

Ulrich

 

[John Hermanson]

It is possible meter is off simply due to the batteries you are using. The OM-2/2N were designed around the silver oxide MS76 type battery (357, SR-44W, G-13, S76, 303). Using alkaline (A76, LR44) or single cell lithium (CR1/3N) are known to cause the very problem you mention. Wrong battery also causes shutter lock (mirror goes up, shutter doesn't fire). If you are using silver oxide and meter is off, it would have to be determined if it is actually off, by testing it against a known calibrated light source (comparing to other cameras is not necessarily accurate). Adjustment of the meter needle position is done completely independently of shutter speeds or actual auto exposure. Adjustments have to be done in this order: Manual 1/1000, manual 1/8th (then all manual speeds are in, then auto exposure at BV12, then needle position in auto at bv12. When BV12 meter adjustment is good, it should be accurate at all light levels unless CDS cells have gone bad (extremely rare). Auto otf silicon blue cells on the mirror box floor NEVER go bad. I'd be happy to overhaul your camera for you if you are interested. John

 

[BetterSense]

I suppose a full CLA is the answer. I will probably put it off until the camera stops working. The auto meter indicator needle is also untrustworthy, since it will indicate like 1/8s but when the shutter fires it's obviously not using 1/8s. However when I actually use auto exposure it is right on. I rarely use autoexposure but since my manual meter needle is not working whenever I'm unsure of the lighting conditions I can always use the autoexposure.

 

[Galah]

... The auto meter indicator needle is also untrustworthy, since it will indicate like 1/8s but when the shutter fires it's obviously not using 1/8s. However when I actually use auto exposure it is right on. I rarely use autoexposure but since my manual meter needle is not working whenever I'm unsure of the lighting conditions I can always use the autoexposure.

This apparent inconsistencey in the visuals on firing the shutter is -initially- highly disconcerting to the OM2n user, but normal behaviour on the part of the camera.

The chief question is: are the negatives correctly exposed?

If so, the camera is working OK.

As has already been mentioned. the camera has a complicated split-personality exposure measuring system: a before and a during the actual exposure.:confused:

Although something of an oversimplification, the camera, effectively, works in such a way that all exposure ends up in real-time automatic off the film exposure: the manual setting gives you an "indicative" reading only. When you press the shutter, the real-time- off-the-film reading (which actually uses another, dedicated, sensor) takes over. What you, as user, see, is the indicator needle doing an inexplicable dip at the point of shutter release. This is normal behaviour for an OM2n. This is so whether you are in "manual" mode or in "auto" mode, it doesn't matter.

If the exposure is correct on "auto" (allowing for the need to dial in exposure compensation for non-standard scenes, as required by the needs of the scene and your "artistic judgement"), it should all be OK.

Make sure you use two 1.5v Silver Oxide batteries.

 

[BetterSense]

The chief question is: are the negatives correctly exposed?

If I use autoexposure, yes. Even slides are well exposed for average scenes. If I use manual exposure with a separate light meter or 'sunny 16', yes. If I use manual exposure and listen to the in-camera meter, no.

I do not like to use autoexposure, especially when I can't tell what shutter speed the camera is going to use (on account of the pre-meter needle being wrong).

 

[John Hermanson]

OM-2/2N Auto shutter speed is read off the film so when testing the camera, either a test card or dummy test film must be at the film plane. Without either of these, the camera reads the light off the black pressure plate and leaves the shutter open too long. John

 

[MattKing]

Although something of an oversimplification, the camera, effectively, works in such a way that all exposure ends up in real-time automatic off the film exposure: the manual setting gives you an "indicative" reading only. When you press the shutter, the real-time- off-the-film reading (which actually uses another, dedicated, sensor) takes over. What you, as user, see, is the indicator needle doing an inexplicable dip at the point of shutter release. This is normal behaviour for an OM2n. This is so whether you are in "manual" mode or in "auto" mode, it doesn't matter.

Galah:

I don't believe this to be correct.

When the OM2 is in manual mode, you get manual exposure. The off the film sensor has no effect on your shutter speed.

The other, in finder sensor does function in manual mode, but only to indicate a suggested exposure.

 

[John Hermanson]

I said :

"OM-2/2N Auto shutter speed is read off the film" hence the phrase "otf". To expand on this: Shutter speeds from 2.5 minutes to 1/45th of a second are read off the film, 1/45th of a second through 1/1000th read off the pattern on the first shutter curtain.

That's auto shutter speed. It is obvious that manual shutter speed is not read off the film.

The meter needle position that is shown in the finder is controlled solely by the CDS cells on either side of the eyepiece lens. The silicon blue cells in the mirror box floor control only the actual off-the-film exposure when the camera is set to AUTO. These floor mounted cells do not control the meter needle position.

Hope this clarifies all. John