Archived posting to the Leica Users Group, 1997/07/14

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Subject: Re: Effect of fungus
From: Joe Berenbaum <joe-b@dircon.co.uk>
Date: Tue, 15 Jul 1997 03:37:13 +0100 (BST)

At 14:22 14/07/97 PST, you wrote:
>     Hi,
>     
>      I just wonder how a developing spot of fungus in a lens affect the 
>     image quality?  Is it critical to clean the lens?  Also does it keep 
>     growing once it started or can it be prevented if it is kept in dry 
>     environment?
>     
>     Thanks,
>     David

This what I've been told; exposure to the UV light in daylight will kill the
existing fungus. Once it's dead it won't grow any more (unless of course you
allow the unsuitable environment that encourages it- fungus spores are
carried in the atmosphere so any lens can theoretically get fungus in
damp/dark conditions). Just take the caps off and open the diaphragm and
leave it in the light for a day or two. Don't worry about the UV light not
getting through the windows- it will. Observe commonsense precautions about
direct sun; don't fry the lens and don't allow its ability to focus light
and heat rays to start a fire! After that, cleaning may be a good idea if
you think the image quality is affected. Do not store lenses in damp dark
places.

Joe Berenbaum