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  1. #1

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    Metering on Olympus OM-1.....Way off!!

    (Kindly let me premise this post with a special thank you to our own Jon Goodman (Interslice light seals).Without his assistance I would not have been able to figure out the method of resealing this particular camera.It was prompt and it was free.)

    Newly resealed,mint cosmetics but my recently acquired OM-1 meters terribly.It is totally out of whack when compared to my Nikon FE2.
    What should I look for?

    Mike

  2. #2
    E76
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    Is the battery fresh? The OM-1 was designed to use mercury cells, which do not exhibit the voltage fluctuations that the alkaline batteries do. The OM-1's metering system is very sensitive to these fluctuations. In order to ensure accurate metering at all times, you can either have your camera converted to use alkaline cells, or use a zinc air battery such as a Wein cell. Zinc air batteries have a discharge curve very similar to the old mercury cells.

  3. #3
    lxdude's Avatar
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    It can be adjusted to use silver oxide cells too, right? More stable voltage curve than alkalines.
    I do use a digital device in my photographic pursuits when necessary.
    When someone rags on me for using film, I use a middle digit, upraised.

  4. #4
    Steve Smith's Avatar
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    To use silver oxide cells it will need either an adptor with a schottky diode to reduce the voltage or the camera can be modified to have the diode fitted internally in series with the cell connection.


    Steve.

  5. #5
    lxdude's Avatar
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    I thought there was a potentiometer to adjust the meter. Guess not.
    I do use a digital device in my photographic pursuits when necessary.
    When someone rags on me for using film, I use a middle digit, upraised.

  6. #6

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    Quote Originally Posted by Mike Kennedy View Post
    I would not have been able to figure out the method of resealing this particular camera.
    Sorry, no help with the metering. But you should know that you'll find the same goo to which the lightseals degraded inside the camera around the prism. It will eventually destroy the prism so this should be changed too. May be you could talk to John Hermanson from zuiko.com about a CLA. The camera is worth it.

    Ulrich

    PS haven't seen that you are located in England. So you might consider Frank Timmann at om-doctor.de. There may be someone knowledgeable in UK too of cause.

  7. #7

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    Alkaline battery creates non-linear readings. Camera can be converted to use silver oxide battery (ms76 type). There is no potentiometer inside for adjustment. Fine adjustment is done with eccentric. Use open cell foam for resealing. John

  8. #8
    lxdude's Avatar
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    Quote Originally Posted by John Hermanson View Post
    Alkaline battery creates non-linear readings. Camera can be converted to use silver oxide battery (ms76 type). There is no potentiometer inside for adjustment. Fine adjustment is done with eccentric. Use open cell foam for resealing. John
    So the galvanometer has its own adjustment, right? Heck, IMO that's even better. If that's the case, then adjustment could easily be done along with other service.

    Or does eccentric refer to the repairman?
    I do use a digital device in my photographic pursuits when necessary.
    When someone rags on me for using film, I use a middle digit, upraised.

  9. #9
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    Time ago, for little money, I bought a used OM-1 in excellent cosmetic condition excepting the leatherette and seals (I thought). Interslice (Jon Goodman), CameraLeather (Morgan Sparks) and a C.R.I.S. adapter took care of the easiest part of the overhaul/update.

    But I had a similar problem with a grossly misaligned (but working) light meter. After fumbling for a while, I realized that someone (not me) had mounted incorrectly the ASA indicator disc on the ASA dial. So, when I set a film speed of ASA 400, the camera calculated an exposure for a, let's say, ASA 25 film.

    Check if meter readings are self-consistent (speed vs aperture) and repeatable, if so, there is a possibility that you are having the same problem. Its very easy to mount this disc, just glued to the dial, in any position you want, but only one is correct.
    Last edited by MPandolfo; 07-28-2010 at 01:17 PM. Click to view previous post history.
    Marcelo
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    The harder I work, the luckier I get.

  10. #10
    CGW
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    I'd check at photo.net(search "PX-625" or "mercury cells")for a trove of info on how to cope without merc cells. Given the dearth of capable repair guys in 2010, I'd try using zinc-air cells rather than risk totally botching the meter with "recalibration" surgery. As long as you stick to C41 films their huge exposure latitude will cover your Oly's meter being off a stop+/-. Few cameras that age escape age-related metering issues, so as long as it's off but linear you'll be OK.

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