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OM-4 Exposure Dial

  1. markmfredrickson
    I'm getting an OM-4 up and running again, but I am having a problem with the exposure compensation. The symptoms are as follows:

    • When the dial is set to 0 compensation the +- indicator continues to light in the viewfinder (most of the time - see next item).
    • Sometimes turning the compensation dial up or down does eventually find a location that registers as 0 compensation and the +- indicator goes out. This location is rarely the zero mark.
    • Changing the ISO/ASA setting does appear to change the suggested shutter speed (e.g. if it is at 1/125 at ISO 200, setting to ISO 400 bumps shutter speed to 1/500)
    • Changing the compensation dial does not always have a noticeable effect even though +- is lit. Sometimes the metered values do change, other times they do not.
    • I can see a small white tab under the dial near the front of the camera. It seems to move back and forth with changing ISO and/or compensation but I don't see a consistent pattern.
    • The dial is not perfectly flat, it slopes away from the white tab mentioned above.


    Has anyone seen this issue before and knows of a solution? I suspect the answer will be send it to John H. This is certainly good advice, but if there is something I can do, I'm willing to try.
  2. bluedog
    bluedog
    If the small white tab is under the ASA dial it should be aligned with the zero of the + or -exposure compensation after the ASA is set. Sometimes aligning this will alter the ASA setting and you will have to set the ASA again and realign the white tab. It normally only takes one or two goes to get it to match the zero point. See if that helps with the viewfinder display.
    Greg
  3. markmfredrickson
    markmfredrickson
    Thanks for the notes Greg. What you describe is normal operation, my situation was a little more involved. Here's the solution (I hope):

    The white tab to which I refer is a small piece of plastic that connects the ASA/ISO/Compensation dial to the electronics underneath (a variable resistor I believe, from reading the service docs). It sits at the front of the camera and moves between approximately 10 o'clock and 2 o'clock. Unsurprisingly, at 12 o'clock, the camera registers zero exposure comp.

    Under normal circumstances, one cannot see this tab as it is in a small cut out in the ISO dial. In my case, the it had come out of the cut out (thus the dial was pushed up slightly at the front of the camera because the dial was sitting on the tab). To fix it, I removed the lock nut on the film rewind post to free the ISO dial. Be careful, there is a small brass piece and a screw that wish to leap to freedom when the cover with the ISO speeds is removed. (I hope I got these back in the right place.) At this point I noticed the cut out and was able to slip the tab into the cut out so that the dial sits flat. To reassemble, the ISO speed disc has a cut out that slots on to another tab, and the knurled dial with window sits on top. Reattach the lock nut and you are done.

    I suspect this could be done without the disassembly. By lifting the knurled knob and sliding the EV tab to 12 o'clock, it might just slip back into the dial. But I didn't know this until I did some surgery on my camera.

    The camera now consistently registers zero compensation when the dial is turned to the appropriate position. The sunny f/16 rule indicates that the meter is using the ISO speed I see in the window.

    Now to pass a few rolls of film through it!
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