Mamiya 645j metered Prisms- Differences?

Discussion in 'Medium Format Cameras and Accessories' started by rrankin, Oct 29, 2011.

  1. rrankin

    rrankin Member

    Messages:
    866
    Joined:
    May 27, 2005
    Location:
    La Plata, Mi
    Shooter:
    Large Format
    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. atomicthumbs

    atomicthumbs Member

    Messages:
    23
    Joined:
    Feb 1, 2011
    Shooter:
    Medium Format
    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. JohnMeadows

    JohnMeadows Subscriber

    Messages:
    312
    Joined:
    Jul 27, 2010
    Location:
    Toronto, Ont
    Shooter:
    Medium Format
    I use the PD version on my 645J and 1000S and it works quite well; quite accurate.
     
  4. snederhiser

    snederhiser Member

    Messages:
    162
    Joined:
    Oct 14, 2010
    Shooter:
    Medium Format
    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. rrankin

    rrankin Member

    Messages:
    866
    Joined:
    May 27, 2005
    Location:
    La Plata, Mi
    Shooter:
    Large Format
    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. brucemuir

    brucemuir Member

    Messages:
    2,265
    Joined:
    Dec 25, 2007
    Location:
    Metro DC are
    Shooter:
    Multi Format
    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. lensman_nh

    lensman_nh Member

    Messages:
    45
    Joined:
    Nov 18, 2010
    Location:
    New Hampshir
    Shooter:
    Multi Format
    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. snederhiser

    snederhiser Member

    Messages:
    162
    Joined:
    Oct 14, 2010
    Shooter:
    Medium Format
    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. rrankin

    rrankin Member

    Messages:
    866
    Joined:
    May 27, 2005
    Location:
    La Plata, Mi
    Shooter:
    Large Format
    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. hnrh2

    hnrh2 Member

    Messages:
    16
    Joined:
    Sep 23, 2010
    Shooter:
    35mm
    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
     
  11. rrankin

    rrankin Member

    Messages:
    866
    Joined:
    May 27, 2005
    Location:
    La Plata, Mi
    Shooter:
    Large Format
    Thanks. I have pretty much decided that I want the metering but don't need the auto-anything, so will likely go with the PD prism.
    Richard