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Re: [OM] OM2n

Subject: Re: [OM] OM2n
From: "John A. Lind" <jlind@xxxxxxxxxxxx>
Date: Mon, 09 Jun 2003 01:49:39 -0500
Ajai,
You must have film in the camera for the TTL-OTF auto-exposure system to function correctly. What you see in the viewfinder comes from one metering circuit in the prism and it tells you what to expect. Actual exposure control occurs *during* exposure by measuring light reflecting from the film. If there's no film in the camera, it's measuring the light being reflected by the film pressure plate mounted on the camera back, which is much less reflective than film. This *will* cause significantly longer shutter speeds compared to what the viewfinder meter shows. Loading the camera with a "test roll" of film should cure this . . . as I believe you have already discovered. BTW, for shutter speeds 1/60th and faster, the curtains also have a white dot pattern that approximates the reflectance of film.

I recommend avoiding alkaline batteries. They do not last long in OM camera bodies due to their voltage falloff that starts at about half-life. This is inherent to alkaline batteries. Even though the battery box and owner's manual calls for SR44 cells, I use #357 silver oxide watch batteries. They're essentially the same (#357 = SR44W) and often easier to find than silver oxide camera batteries. The slightly different characteristics of the #357 watch battery also seem to make them last longer in the OM SLR's. Other alternatives include #303 watch cells and MS76 (Duracell), EPX76 (Eveready), or V76PX (Varta). All of these are silver-oxide.

With an OM-2n, remember to turn it OFF when it's not being used. Otherwise the meter circuits will remain powered up and drain the batteries.

-- John

At 10:46 PM 6/8/03, Ajai wrote:
 Hi,
I have just bought a old OM2n with few lenses. I was a bit confused with the way the meter works. Or rather the way exposure takes place. In the auto mode, in low light condition, the viewfinder information does not match with the actual exposure. i.e, the exposure time (shutterspeed) is much more than the shutter speed shown in the viewfinder. This I have been able to notice only for the low light condition. I posted this question in the 'photo.net' and have got a very helpful reply. That is, I have been experimenting this because there was no film in the camera. I believe there is something called OT-F which will calculate the exposure overriding the viewfinder information. Please any of you could throw some light on this subject. I tried the same experiment with the film inserted and now it is giving more or less the same exposure as per the viewfinder. But still about ! 1 or 1.5 seconds difference in very low light situation. I need another information - is it ok to use LR44 (alkaline)battery for OM2n as Iam unable to get SR44 (silver oxide) batteries. With thanks. Ajai


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