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  1. #1
    ContaxRTSFundus's Avatar
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    Mamiya (645) - 500 f8 focus problem

    Hello all,

    Just acquired this lens and apart from a tiny amount of fungus behind the fornt element (anyone know if it's easy to remove the element?) I have a big problem with the focusing mechanism. The ring moves way past infinity and fails to let the lens focus to its stated minimum distance. Does someone know whether this is a DIY job to correct or am I looking at a professional repair? And with fungus present, I understand some repairers won't accept such lenses...

    Thanks for any advice.
    Last edited by ContaxRTSFundus; 12-18-2009 at 07:58 AM. Click to view previous post history. Reason: wrong spelling

  2. #2
    keithwms's Avatar
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    I have the 500/5.6 lens, is that the one you mean? I am not familiar with the 500/8. Is it a mirror lens?

    Anyway the problems you describe sound tolerable. That the ring moves past infinity isn't such a big deal, but if you want near focus, I have always used an extension tube for that anyway. As for the fungus, I do think the front element can be removed but it's probably best done by a professional. To kill the fungus is easy enough... with UV light, but cleaning off what's there may require some careful surgery...

    http://www.mypentax.com/Fungus.html

    I'll just add, I recall that in viticulture, it is common practice to burn a sulfur stick in the barrel to kill bacteria, mold, and maybe also fungus.

    Do bear in mind that the 500/5.6 lens in good condition often goes for ~$600-700.
    Last edited by keithwms; 12-18-2009 at 08:14 AM. Click to view previous post history.
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