Q: What Are The Facts About "FUNGUS" In A Camera Lens?

Here is my answer to this member's question:A: Dear okay Member,Fungus
is caused by a gebination of moisture and dust (containing fungus spores) inside the lens. Some
dust gets inside every lens that isn't fully "weather sealed" (like an
expensive "L" professional model). When
moisture gets inside your lens, either because of direct moisture
exposure or
simply because of very high humidity in your local climate, fungus can
begin to grow. Some lenses that I have examined from very humid
"tropical" areas have had the worst cases of fungus
growth that I have seen. (Not all of them, of course, but there is a
slightly
higher percentage of lenses from these areas that have been affected.)A
very unusual problem is caused when lenses are exposed to extreme cold
and then brought into a warm building. The moisture inside the cold
lens condenses into liquid water or "fog" on cold interior lens surfaces,
especially when it is allowed to warm too quickly. The best way to
control this is to leave the lens in its closed protective case and allow
it warm very slowly after is brought inside from sub-freezing conditions.Overall, the
best way to control moisture is to keep small packets of "Silica Gel"
desiccant inside the case with each lens. (Most new lenses gee with a
Silica Gel packet inside the box. Keep it and use it!)When moisture finds its way
inside the lens, it provides a rich medium for the fungus spores that
are often mixed in with dust particles (remember, they were already inside the
lens). The fungus then begins to grow and it multiplies in the moist environment. If this problem is
recognized quickly, a professional lens technician can clean it.
If it is allowed to multiply over time, it causes permanent "etching" in the lens
coatings. This condition is not usually reversible and often
permanently affects the image quality of the lens.The
preferable solution is PREVENTION. However, if you find the signs of
fungus when you look through your lens, have it inspected by a
professional at as soon as possible. Hopefully, you can have it cleaned before the problem begees more serious.Thanks for your very interesting question!Best Wishes,DavidIntroduction To The Q