Contax zoom exposure value declines from center-weighted to spot metering

Discussion in '35mm Cameras' started by Paulukas, May 29, 2004.

  1. Paulukas

    Paulukas Guest

    I've got a Contax ST and the Zeiss 100-300mm f/4.5-5.6 zoom lens.
    Needless to say, it produces beautiful, sharp images. The problem (or
    situation) is this: When using this lens and switching from
    center-weighted metering to spot metering, the exposure value declines
    by 1/2 stop at 100mm and up to 2 stops at 300mm. I've tested this
    several times, using a tripod and pointing the camera at an evenly
    illuminated, blank surface. I understand that there is light falloff
    when zooming from 100mm to 300mm, hence the designation of f/4.5-5.6.
    This is not the problem I'm talking about (the exposure value does
    correctly decline as I zoom out). The issue here is that without
    changing the focal length, the exposure value declines when using spot
    metering. For example, at 300mm, center-weighed will indicate 1/250
    and f/8 whereas spot metering indicates 1/60 and f/8, and all I've
    done is flip the metering switch.

    Can anyone explain this phenomenon? Have you ever heard of this? Do
    you have access to another 100-300mm lens and a spot metering Contax
    (preferrably an ST) to conduct a similar test? This phenomenon does
    not happen when using either my 100 f/2 or my 35-70mm f/3.4 (which
    retains its f/3.4 maximum aperture throughout its zoom range). Also,
    the 100-300mm lens, when used at 100mm, does match the exposure value
    of the 100mm f/2 when both use center-weighted metering.

    Weird, isn't it!? Thanks for any insight you may have.

    - Paul
    Paulukas, May 29, 2004
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  2. Paulukas

    Bob Hickey Guest

    Just a guess here, but is it possible that the exposure lock is on, or
    stuck? Does it do the same thing in manual and auto, or all the modes?
    Bob Hickey
    Bob Hickey, May 30, 2004
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  3. Paulukas

    Paulukas Guest

    This occurs in all modes and the AE lock is off.
    Paulukas, Jun 2, 2004
  4. Paulukas

    Barney Guest

    (Paulukas) wrote in
    Is the subject you are pointing to lit the same all around the viewfinder?

    Barney, Jun 8, 2004
  5. Paulukas

    Paulukas Guest

    Yes, the subject is evenly illuminated all around the viewfinder.
    Paulukas, Jul 9, 2004
  6. Paulukas

    Barney Guest

    (Paulukas) wrote in

    That IS weird!!!!

    Barney, Jul 10, 2004
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