Fungus is an ever-present danger to optical equipment. This post describes the threat to our precious kit …

The likelihood is that you, dear photographer, will have fungus-affected equipment, whether that be lenses, camera prisms, mirrors or viewfinders, especially if you live in the tropics (even here in the UK, the climate is becoming more humid). The fungus infection might be too small to see without a microscope, but I wager it is there, waiting for a propitious period of undisturbed time. The problem is the most grave for lenses, as these tend to be the most expensive bits of kit owned by photographers, but other elements of a camera are also at risk.

I have 14 lenses that I treasure with a few that I am less bothered about.

Some of my better lenses (Hasselblad, Rodenstock, Schneider, Leica, and Voigtländer), kept in the light and in an airy place. (This radiator, below the lenses, is never on).

Lenses are always open to fungal spores that float in the air. Given the right conditions, they digest organic material on the lens (mites, oil from your fingerprints, small flecks from paper or cloth wipes, lint, wax and so on), and develop hyphae, which grow across the lens. They produce hydrofluoric acid which permanently etches the lens coating and the underlying glass. Such damage is irreparable.

A while ago I carefully checked each of my lenses for fungal growth. I found that one of my old cheap lens had extensive fungus, but no fungus on my valuable lenses.

Fungal hyphae at the bottom edge of my old Vivitar lens
Fungus growing down from the lens edge, the hardest part of the lens to clean

I tend to use my best lenses quite often and clean them with lens fluid on a monthly basis. Perhaps this has prevented the ever-present fungal spores from developing. Up until then, I had stored my lenses in a dark cupboard, each in its own lens case. Some had silica gel pouches. It turns out that storing them in this way is a mistake. Fungus loves dark, humid, still, and warm conditions. The inside of this particular cupboard is dark, humid, still and warm!

Here are some tips for preventing fungal growth:

  • Dry lenses after each outing if they get damp or wet. Clean lenses gently with fluid taking care to remove any organic matter on the lens surfaces. I do this monthly. (Over-vigorous cleaning can damage the lens coating).
  • Keep lenses in a dry, cool place with plenty of air circulation and open to sunlight
  • If you want to keep dust off them, place them loosely under a cloth cover. I prefer to keep them open to the light.
  • If you use silica gel pouches, dry them in the oven once a week. They become useless if you don’t.
  • If you have an infected lens, throw it away or keep it away from your other lenses.

All common-sense. Check your lenses and cameras!

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