Ajai-- Congratulations on a great camera... the OM-2n is one of my favorite
models.
The OT-F is measuring the light level -as it falls during exposure- on the
film. This is possible because as the light hits the film, some is reflected
back into light sensors on the bottom of the mirror chamber. If you open the
back of the camera with it set on "B" and trigger the shutter you will see
the light sensors. The surface of most films, regardless of the color (light
or dark tan, beige, bluish-purple, etc) reflects close to the same amount of
light. This is more reflective than the film pressure plate, which is black.
So when you use automatic exposure without film in the camera, the OT-F
measuring is getting less light than it would with film in the camera,
making the actual exposure time very long.
The time indicated in the viewfinder is measured by -different- light
sensors located in the viewfinder prism area, and that indication is
intended to be only a guide to the actual automatic OT-F exposure, but that
guide is only accurate with the actual exposure with film in the camera. It
soundsl like your camera is working correctly... put some film in it and
enjoy!
--
Jim Brokaw
OM-'s of all sorts, and no OM-oney...
on 6/8/03 8:46 PM, ajai krishnan at ajaikrishnan@xxxxxxxxx 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 LR!
> 44!
> (alkaline)battery for OM2n as Iam unable to get SR44 (silver oxide) batteries.
> With thanks. Ajai
>
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