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Thread: Fungus

  1. #11
    copake_ham's Avatar
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    Quote Originally Posted by David H. Bebbington View Post
    Not to tread on Dan's toes, but as I understand it, almost all zoom lenses change focal length by moving a central lens group back and forth. This means that the volume of the internal air spaces within the lens change and in turn means that a lens has to have some small breather holes (otherwise you couldn't work the zoom). This opens the way for air to enter the lens. If this air is humid, haze may form. If it is dirty (tobacco smoke, etc.), the haze may be more persistent and will not disappear when the lens is warmed up. Mold spores are I believe frequently present in the air, if they enter the lens through the breather holes and are then left in warm humid conditions, mold growth will result.

    I try to combat mold by not buying second-hand lenses with any visible speckles inside, by storing lenses in cases or plastic bags with silica gel sachets, and by drying gear carefully if it has been out in damp conditions. Many times I ahve driven home from a landscape shoot with the car heater up full and the camera bag open on the passenger seat. In poor conditions I usually carry a towel and wrap the camera in the towel immediately if any water drops fall onto it.

    Regards,

    David
    David,

    Thanks. While we should also let Dan respond, your advice seems "spot on".

    The "smoker" thing would seem to be much more problemattic than humidity and, given the likely age of the lens and the prevelance of smoking back then - is really good cautionary advice.

    I'll certainly keep it in mind if/when I'm fishing around for used zooms.

  2. #12

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    George, David answered your question pretty well but didn't mention lubricants. Some of the lubricants used in focusing helicals and leaf shutters will outgas when warm and what comes out can condense on the glasses. Aged LF lenses often suffer from this kind of haze. Unlike the zoom lens that BobbyR was thinking about, many LF lenses come apart easily for cleaning.

    Cheers,

    Dan

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