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  1. #1

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    Mamiya 645j metered Prisms- Differences?

    I got a Mamiya 645j that I'm really liking so far. Thought I'd pick up a metered prism because I keep forgetting my meter and have to guesstimate off the sunny 16 rule. Went to Ebay and there are several available, of course, but I hadn't realized that there are 3 types available - PD, AE and CDS. I have a copy of the manual but don't really see why I would prefer one over another except that the PD has LEDs in it.

    Can anyone give me a brief explanation of why one is preferable over another? Should one be appreciably cheaper than the other types?

    TIA, Richard

  2. #2
    atomicthumbs's Avatar
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    AE: PD prism that can set the shutter speed automatically

    CDs: cheap prism with cheap sensor; takes a long time to react to light changes

    PD: silicon photodiode sensor; accurate and reacts instantly

  3. #3

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    I use the PD version on my 645J and 1000S and it works quite well; quite accurate.
    Nikon 35mm, Mamiya 645 & RB67, Leica IIIb, other bits and pieces

  4. #4

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    Hello Richard;
    I have the AE prism on my 1000s, this is a shutter priority setup. Automatic operation after the shutter selector, film speed, and prism is turned on. Runs off the battery in the camera, so turn off when not in use. I like this setup and is simular to my Canon AV-1, Steven.

  5. #5

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    Steven,

    Can you use it for aperture priority as well, or only shutter priority?Since the front thingo latches onto the aperture wheel, I'm thinking probably only shutter priority and then it moves the aperture.

    So, the PD/ PDS prism is basically the same except it doesn't change the aperture, it just displays what it should be, and you change manually?


    Richard

  6. #6
    brucemuir's Avatar
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    Be advised A LOT of these older mamiya prisms have separation of the prism where the mirror pieces meet due to foam deterioration. This can make a line through the center of the frame in the prism.

    Some can live with it but you can ask the seller if there is a line in the frame in the prism.

  7. #7

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    I have a prism with the line through it.

    It doesn't affect functionality and personally it doesn't bother me, but I can see how some might be put off.

  8. #8

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    Hello Richard;
    AE means automatic exposure. The prism controls the shutter speed, aperature is set manually to bracket the shutter speeds. The PD/CDS prisms are manual control only. Note the shutter speed selector, the circle with the dot is the setting for automatic operation. Steven.

  9. #9

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    Ok, now I think I understand the differences in them, so just have to decide which I need, I guess. KEH seems to have decent prices on all the versions.

    Thanks,
    Richard

  10. #10

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    PDs is better. More precisely, AE is not well designed:
    AE-lock is gotten by pushing constantly on a small white button close to the secondary shutter which makes operation with ae_lock difficult.
    As mentinned earlier it will drain camera batteries if you forget it (which is really annoying).
    Exposure compenstion is difficult to obtain since you need to change film speed.
    The leds in the Pds are nice enough and clear.

    --
    Hervé

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