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  1. #1

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    Mamiya 645 Super AE Prism N Light Meter Problem

    Hi all,

    I picked up a used Mamiya 645 Super with the AE Prism N Light Meter. I shot a roll of film with it and the whole thing came out blank, except for one shot that had the faintest ghost of an image on it. I went back to the camera and found that the light meter doesn't seem to be working right, it keeps blinking "over" and giving me bad readings when double checked against my Sekonic light meter. I did replace the battery when I first got it with an alkaline battery and thought maybe that was the problem, but I just got some silver-oxide batteries (which are what's recommended) and I'm still having the same problem. I've cleaned all of the contacts, double checked to make sure the shutter was firing properly, and that the shutter wouldn't fire with the dark slide in place... nothing.

    Any suggestions?

    Jorge

  2. #2
    chriscrawfordphoto's Avatar
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    The cost to repair is probably more than the cost to buy another. Does the camera work right in manual mode using your handheld meter? I ask because it may be the camera body that is bad, or it could be the prism.
    Chris Crawford
    Fine Art Photography of Indiana and other places no one else photographs.

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    Fort Wayne, Indiana

  3. #3

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    Everything on the camera seems to work fine in manual mode. I haven't actually shot a roll of film since the first one yet, but the shutter definitely changes speeds. I'll try and shoot a roll this weekend in manual, and develop it next week to know for sure. Also, I can't say 100%, but I'm pretty sure the light meter was working fine before I switched the battery out.

  4. #4
    MattKing's Avatar
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    Are you confident that you have set the correct ISO on the film back?

    If you have more than one back, you should check those as well.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  5. #5

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    I was of the opinion that the film speed on the backs was only a reminder for the user and had nothing to do with the meter settings. They are set on the metering head.

    Because the meter keeps blinking and not steady I would think that the metering head is at fault and nothing to do with the film speed setting.

  6. #6

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    hi jorge

    check the aperture ring coupling pin is in place with the exposure meter coupler on the lens.

    i missed this a few times when i first got the same camera,its a silver pin under the mamiya 645

    lable on the front. without this the meter wil not work right.

    al.b

  7. #7

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    Good Morning guys,

    Not sure about the iso setting... I changed it on the wheel on the film back, but I can't see that it made any difference. I don't know any other way to change it, since there doesn't seem to be a spot to do so on the metering head. I did double check the aperture ring coupling pin and it's seated just fine. The meter does stop blinking if I stop the lens all the way down to f/22, but even in a poorly lit room, where my Sekonic is telling me 2/10 of a second, the Mamiya meter is telling me 500-1000. I'm going to check the manual again and see if there's another way to adjust the iso setting.

    Jorge

  8. #8
    MattKing's Avatar
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    To set the film speed, you need to set the wheel on the film back.

    That permits changing between backs loaded with different films "on the fly" without having to worry about adjusting the film speed on the camera.

    As the film backs themselves are involved in the metering system, it is a good idea, if possible, to try another back to see if the problem originates with the back.

    Does switching the metering mode from Average to Spot make a difference?

    Are you sure the lens is set to open-aperture metering ("A") rather than to stop-down metering ("M")?

    Although I think that if it was set to "M" it would give you the opposite problem.

    Finally, are you metering manually, or using Auto-exposure? If Auto-Exposure, which mode?
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  9. #9

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    Hi Matt,

    I set the film speed on the back to the proper ISO, I tried various backs and had the same problem. I also tried changing the film speed to something lower and still had the same problem, even on ISO 25 the light meter kept saying "over". Switching the metering from Average to Spot makes no difference. The lens is set to open-aperture ("A"). I'm using auto-exposure set to the normal AE mode. I also tried it in the AE Lock position, and still got the same problem. If by metering manually you mean that I'm using my handheld light meter and then adjusting the shutter speed, etc... based on that, then no I haven't tried that yet, but I will be doing that this weekend and developing the roll next week to see if the camera works that way which I believe it will. It would just be way more convenient if the auto-exposure metering in the viewfinder worked properly.

    Jorge

  10. #10
    MattKing's Avatar
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    Hi Jorge,

    By manual metering, I mean the following:

    When the shutter speed dial is not set to one of the two AE settings, the meter still works. What should happen then is that the meter causes two shutter speed indicators to flash in the viewfinder - one being the recommended shutter speed, with the other being the one that has been manually set. If they are the same, that is what is illuminated and flashing.

    If that works, but the AE functions don't, that at least tells you something.

    FWIW I've used that prism successfully on both 645 Super bodies and my current 645 Pro body.

    The problem may be as simple as a problem with contacts.

    Hope you can find a solution.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

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