[Leica] Fungus -- humidity? or darkness the catalyst?

[Harry Haige <haige@compuserve.com>]

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Living in the subtropics, I have noticed that it seems to be storage of
things ranging from leather goods to optical equipment in darkness that
promotes growth of mildew/fungus.  Nothing ever seems to happen to shoes I
wear or lenses sitting on a shelf in a well lighted room without caps on
either end, no matter how high the humidity.  Have heard just that advice
from repair shops and old timer collectors.  

Harry