Preventing Fungi on Camera Lenses

One of the most common questions in photography is about how to prevent fungi contamination on lenses and other photographic equipment. The solution is very obvious but there is a lot of misinformation on the internet that must be cleared.

First, know your enemy, the fungus.

• They like dark, humid places.
• Some of them don't care about the light, others do.
• About temperature, depending on the species, they can live from subfreezing arctic to equatorial jungles...

The common ground is the humidity, not the temperature unless we're talking about more than 50 degrees Celsius. Don't believe it? Temperatures in the Amazon rainforest can reach easily 42-43 degrees Celcius and there are LOTS of fungi there. Temperatures in cheese maturation caves are always below 10C and sometimes 5C. Plenty of fungi there... Each fungi strain has a specific optimal temperature range for development. 

Keep the humidity low and you'll make any fungus life much harder.

I use two Benro dry cabinets set to 35% RH and I had no problems with fungus since 15 years ago. You can also use hermetic pots with silica-gel, but you WILL need to heat the silica from time to time, or when the RH goes over 40% inside the pot. Put a small cheap hygrometer inside the pot, container, or whatever you use. The key is to have a good SEALED one. No good sealing = no protection.

About the UV urban legend (UV-C lamps, sunbath, etc.)

Some facts:

• UV-C is dangerous for skin and eyes
• UV-B and UV-C will damage or even destroy rubber parts
• UV-B and UV-C will NOT pass through the optical glass used on lenses. Just some part of the UV-A will pass and UV-A will NOT kill the fungus.

But someone said: Oh, but when I sunbathe my lenses I perceive that the fungus would not grow anymore!

Not so simple. What's messing up with the fungus is the HEATH, not the UV. It's easy to reach temperatures well over +40C under these conditions and this is what is disrupting the fungus growth. But the spores are far more resistant and they will probably survive and grow when the conditions turn favorable.

The only SURE way to kill fungi with UV is to expose the contaminated side of the elements directly to UV-C what means to disassembly the lens and I would not recommend this for obvious reasons. If you reached the point of disassembling the lens to do this, it would make much more sense to use a neutral detergent to remove the fungi, dirty and oil, then use a biocide like Lysoform or a Hydrogen Peroxide solution to kill the fungi and spores, rinse everything with water, dry and reassemble everything. NO NEED FOR UV this is stupid.

About X-Rays, the irradiation time needed for sterilization needs to be massive! That 1s dose from your dentist friend's X-Ray machine will do NOTHING and will just be a waste of the X-Ray emitter's life.