Dim viewfinder image with faster lens?

Discussion in '35mm Cameras' started by sreenath, May 10, 2005.

  1. sreenath

    sreenath Guest

    Hi All,

    I have old screwmount cameras, and have collected a good number of
    normal lenses.

    Of interest here is the Mamiya/Sekor 55mm 1.4.
    When this is mounted on a camera, the image in the view finder is
    dimmer than Fujinon 55mm f/2.2, which is more than one stop slower
    then the 55/1.4.

    Yashinon 50mm f/2 also produces a brighter image in the viewfinder.

    I am preplexed by this. The mamoya sekor lens is not in great shape, of
    Also, the coating on Fuji lens seems to be better than the Mamiya

    The elements of the Mamiya seem to be quite yellow/amber in color. Can
    this be causing this to happen? I dont know if this is the coating
    color or the elements themselves have become yellow.

    If this is the cause, is there anything that can be done to
    reduce/remove the yellow coloring?

    sreenath, May 10, 2005
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  2. It could be that the lens is trasmitting less light because of the
    yellowing you mentioned or haze, which will reduce the transparency of
    the lens.

    Another possibility is that the lens diaphragm doesn't open all the way,
    i.e. that it stays closed to f/2.0 or 2.8, either through a defect in
    the lens or because of the lens-camera combination: Look into the lens
    mounted on the camera to see if the diaphragm is wide open.

    Third possiblity is that some lens designs just seem to result in much
    darker viewfinders than their effective apertures would produce. I've
    noticed this in most/all old-style very retrofocus super-wideangle
    lenses (i.e. those 20 & 25mms with the huge front elements), though not
    in longer lenses.
    If they are yellow while looking through the lens, then the elements are
    yellow (this happens to many lenses using radioactive glass elements).
    It can't be "cured", but if the yellow appears on the photographs, you
    can use a light warming filter.
    Chris Loffredo, May 10, 2005
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  3. sreenath

    Colin D Guest

    This yellowing also happened to some Pentax lenses with radio-active
    elements. Somebody at the time mentioned that leaving the lens in
    direct sunlight for a few days appeared to bleach out the yellow.

    Colin D, May 11, 2005
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