Archived posting to the Leica Users Group, 1996/11/05

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Subject: Re: Hektor 135mm 4.5 Fungus
From: D Khong <dkhong@pacific.net.sg>
Date: Wed, 6 Nov 1996 06:21:08 +0800 (SGT)

At 02:07 PM 11/5/96 +0100, you wrote:
>Forgive my ignorance. I never have seen fungus on a lens and I
>don't want to be surprised by it when a buy one. Is it obvious
>at first sight or do I have to look carefully?
>
>What can I do to save my own lenses?
>
>Regards, Rainer

Fungus generally start growing on lenses when the relative humidity is high.
I stay in the tropics where the R.H. exceeds 80% most of the time and fungus
really love such atmospheric conditions.

They usually start insidiously.  Their appeareance is like  cotton hair
spots which spreads from a central spore deposit. Some start at the
periphery.   You have to look through the lens wide open against the light
and check out every element. Once seen, never forgotten.  Early growth can
be easily cleaned by a repairman.  Advanced growth can destroy lens coating
and cause pitting of the glass.

To prevent growth, all new lenses shpuld be kept in a dry box - silica gel
or one of those new electronic dry cabinets (which comes with a hygrometer)
with settable RH control).

Dan
Singapore.