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  1. #11
    RH Designs's Avatar
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    Remember the OM10 has two metering systems, one in the viewfinder which is for displaying exposure information only, and the OTF (off the film) metering system which controls the actual exposure and only starts working once the shutter has been released. If your negs are correctly exposed then the OTF system is working OK. During the actual exposure the mirror is up and so the viewfinder meter can't see anything - hence the change in the displayed exposure.
    Regards,
    Richard.

    RH Designs - My Photography

  2. #12

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    Quote Originally Posted by RH Designs View Post
    Remember the OM10 has two metering systems, one in the viewfinder which is for displaying exposure information only, and the OTF (off the film) metering system which controls the actual exposure and only starts working once the shutter has been released. If your negs are correctly exposed then the OTF system is working OK. During the actual exposure the mirror is up and so the viewfinder meter can't see anything - hence the change in the displayed exposure.
    Well it's just that it doesn't seem to happen with my other makes of cameras.

  3. #13

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    Quote Originally Posted by Galah View Post
    Well, waddya know!:o You're right, Excalibur2, the viewfinder reading behaves exactly as you have pointed out (above). I'm amazed I hadn't noticed this before!

    However, the negatives seem to come out exposed OK, so it can't be a problem (at least, so far).
    Well I have the OM20 as well as the OM10, and it moves more than the OM10, but I have never put a film in the OM20 (after the lenses in an auction and got it as an extra) as I've switched to Canon and Konica.

  4. #14
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    Quote Originally Posted by Excalibur2 View Post
    Well it's just that it doesn't seem to happen with my other makes of cameras.
    It won't, because of the way the Olympus OTF system works. Most auto SLRs take a light measurement before the exposure and use that to calculate the time and/or aperture, so the reading doesn't change when you release the shutter.

    Olympus auto SLRs measure the light during the exposure and so are able to adjust it if the light level changes during a long exposure, but because viewfinder info is provided by a separate metering cell in the viewfinder, while the mirror is up it cannot provide a reading. Hence the "dip" in the reading during the exposure. Later Olympus auto SLRs, from the OM-2SP and OM-4 onwards, use a semi-silvered mirror and a single metering cell which provides both exposure and viewfinder information.
    Regards,
    Richard.

    RH Designs - My Photography

  5. #15

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    Quote Originally Posted by RH Designs View Post
    It won't, because of the way the Olympus OTF system works. Most auto SLRs take a light measurement before the exposure and use that to calculate the time and/or aperture, so the reading doesn't change when you release the shutter.

    Olympus auto SLRs measure the light during the exposure and so are able to adjust it if the light level changes during a long exposure, but because viewfinder info is provided by a separate metering cell in the viewfinder, while the mirror is up it cannot provide a reading. Hence the "dip" in the reading during the exposure. Later Olympus auto SLRs, from the OM-2SP and OM-4 onwards, use a semi-silvered mirror and a single metering cell which provides both exposure and viewfinder information.
    Ah..thanks.

  6. #16

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    Quote Originally Posted by RH Designs View Post
    It won't, because of the way the Olympus OTF system works. Most auto SLRs take a light measurement before the exposure and use that to calculate the time and/or aperture, so the reading doesn't change when you release the shutter.

    Olympus auto SLRs measure the light during the exposure and so are able to adjust it if the light level changes during a long exposure, but because viewfinder info is provided by a separate metering cell in the viewfinder, while the mirror is up it cannot provide a reading. Hence the "dip" in the reading during the exposure. Later Olympus auto SLRs, from the OM-2SP and OM-4 onwards, use a semi-silvered mirror and a single metering cell which provides both exposure and viewfinder information.
    Dear RH Designs,

    Well, you learn something new every day!

    Thanks for this useful piece of information. I must say, without it I would have tended to worry: unnecessarily, as it turns out.

  7. #17
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    Quote Originally Posted by Galah View Post
    Well, you learn something new every day!

    Thanks for this useful piece of information. I must say, without it I would have tended to worry: unnecessarily, as it turns out.
    Dear Galah,

    You're welcome . And something else you maybe don't know - the OM10 doesn't even have to be switched on to make a correctly exposed photograph! The "on" switch just enables the v/f meter. If you press the shutter release, the mirror rises and switches on the OTF metering system which then computes the exposure and closes the shutter at the appropriate time.

    If you don't already have it I'd recommend getting a Manual Adaptor for your OM10, it gives you more control and is easier to use than the fiddly exposure compensation dial.
    Regards,
    Richard.

    RH Designs - My Photography

  8. #18

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    Behavior is normal for OM-10 (and G, PC, OM-2 etc.) OM-10 meter display you see in teh viewfinder is read off the focus screen which is at a certain brightness when you look at a scene. When you fire the shutter, the mirror goes up, finder gets dark, LED reading goes down. Light is read off the first curtain / film, shtter opens and closes, mirror comes back down, finder gets bright again, LED goes up. Hope this helps. John, servicing OM since 1977.

  9. #19

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    Dear John and Richard,

    Thank you both for your input.

    Having heard from you about the behaviour of the OM10, I naturally checked out my OM2n, which appears to do the same, as John suggests (above), though not as obviously.

    Richard, I do have the Manual Adaptor and do intend to use it because, as you say, EC is rather fiddly on the Auto setting. Its just that I haven't yet got around to it. I will do it with my next film.

    Also, its interesting that the camera is designed to operate, even if the selector switch is in the "off" position. This is a great "battery saver" feature. Does this also apply if using the power winder?

    Thanks.

  10. #20
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    I don't know the answer re the power winder I'm afraid, I've never used the two together.

    I found the OM-10's metering rather sensitive to bright skies which is why I got the manual adaptor, to reduce the likelihood of under-exposure. The OM-2n seemed less sensitive so presumably has a more "centre-weighted" metering pattern.
    Regards,
    Richard.

    RH Designs - My Photography

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