Olympus OM-1 light meter skewed

Discussion in '35mm Cameras and Accessories' started by aaronmacdonald, Apr 11, 2012.

  1. aaronmacdonald

    aaronmacdonald Member

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    I've noticed when using my Olympus OM-1 slr that to get a proper exposure I need to adjust the camera settings to be usually 2-3 stops larger (or shutter speeds longer) than what the light meter is telling my to expose at. Therefore the light meter's needle, instead of resting evenly between + and -, has to be at or past +. Could this indicate a battery problem? Such as the battery losing energy or being the wrong voltage? Or is it problem with the meter itself?

    I'm using a 625A button cell battery. I can't recall when this began or for how long it's been happening as the OM-1 is not my primary camera.

    Thanks
     
  2. E. von Hoegh

    E. von Hoegh Member

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    625A is an alkaline cell, correct? If so, it's likely the fact that an alkaline cell gives almost 1.6v, and your meter is designed to operate on 1.35v. A higher voltage leads to underexposure.
     
  3. thuggins

    thuggins Member

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    Get an MR-9 adapter or send it to John Hermanson for a CLA. He will modify it to work with a silver oxide cell as a standard part of the tune-up.
     
  4. Pumalite

    Pumalite Subscriber

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    You can also use 2 Air Zinc batteries and a rubber O ring aroud to fill the space. If the rubber doesn't work; use a metal O ring ( cut it from a spring of the proper size. I personally prefer a handheld meter.)
     
    Last edited by a moderator: Apr 11, 2012
  5. mgb74

    mgb74 Subscriber

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    Much has already been written, so I won't go into too much depth. Basically, your OM1 was designed to operate on at 1.35v battery (mercury) that pretty much stays at a constant voltage until it fails. Your 625 battery is alkaline, starts at 1.5v or 1.55v and declines with use. So it could be providing too much voltage, too little, or just the right amount depending on where it it in the voltage curve.

    Info at http://www.kyphoto.com/classics/mercurybattery.html

    But 2-3 stops is more than I've encountered using an alkaline battery, so there may be a meter issue too.
     
  6. mr rusty

    mr rusty Subscriber

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    As others have said.

    Where abouts in the world are you? If US, then John Hermanson is the man to go to. In the UK I recommend Michael Spencer at camerarepairs-r-us.co.uk. He will check out your meter and modify it to take SR44 cells. In fact, my OM1 had a similar issue - the meter was reading way out and Michael found a dry joint on one of the soldered connections which he sorted. I've had 3 OMs serviced by Michael now and have been pleased every time.
     
  7. John Hermanson

    John Hermanson Member

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    625A cell is 1.55V and causes up to a 3 stop error in OM-1/1N. Battery is also non linear (different error at different light levels). When I convert an OM-1, I do so with a silver oxide 1.55V battery and schotkey diode. This is a linear setup and accurate. John
     
  8. nsurit

    nsurit Subscriber

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    John is the "Man." having dome much very satisfactory work on my OMs over the years, Bill Barber