Why does fungus form in lenses, and how to get rid of it?

I hate to say it, but the best thing that can be done is to get rid of it. Especially a lens like a 50mm f/2, it shouldn't cost very much at all to replace it. There isn't a good way to clean the middle elements of a lens.

You've already mentioned the green spot, it'll cause enough problems.

You can minimize fungal growth by protecting from the elements (Especially water), making sure to use it periodically, etc.

The only course of action here is to get the lens professionally serviced. Once mould spores have got into your lens and started to grow like this there is no other way to get rid of them. In order to prevent this in the future always store your camera in a sealed bag with a couple of sachets of silica granules to absorb any moisture that may have got into the camera during use. This is especially important if you're in very humid environments or if the camera has got at all wet.

I recently saw on YouTube - BTW an interesting place for instructions and answers - that you should never store cameras or lenses in camera bags. The fabric in the bag is a great place for mold spores to get imbedded. So dark, moist places surrounded by lower grade of fabric invites disaster. It was suggested when cameras and lenses not in use to put them in an air-tight, transparent, plastic or acrylic case with silica gel. To recap what invites disaster: fungus needs heat, damp and darkness to thrive.

Addendum: Do not store a lens with mold together with other lenses! Also don't attach a lens with mold to your camera, it might contaminate all of your gear.

To protect against contamination, Zeiss only allows lenses without mold into its service centres. [p.85, c't Digitale Fotografie 04/2013]

Fungus is just a biological, er, thing, which will grow when the conditions are right.

Sorry for the vague information, I just wanted to say: untreated fungus can etch the coating on your lens and therefore damage it permanently. Better do something about it.

Generally fungus (just like mushrooms) will grow best in dark, damp, stale but not-to-cold environment. I don't know if there is a specific type that grows on lenses.

If I was you, this is what I would do:

1. Regularly use and expose the equipment to sunrays (UV). The aim is to:
   1. dry any condensation
   2. kill fungus through exposure
   3. circulate the air and avoid fungus growth.
2. When not using it (see above), prevent fungus by storing the equipment in a dry place. You can sachets of silica gel or even sachets of rice to absorb moisture and keep the air dry in your camera boxes / bags.

Ad 1a : What kind of "food" does it find in a glass element?

Dust. There is dust inside your lenses. It's almost never visible on the photos, sometimes you can see some of it by shining flashlight from the other side, but the dust is there. Some of it is biological (including fungi spores) and this is what fungus eats. This is why it's so important to control humidity; both food and spores should be considered as already in place so water supply is the only thing owner can control.

Damp in the air is the worst factor. Anything over 60% humidity is enough for the spores to germinate, and ruin your camera... I've seen mould that has encompassed the entire camera before now, when I bought an old Zenith that had been stored in an old, canvas tent... That's actually made my flesh crawl, to remember that! I am curious to know which types of mould are the most common, in camera lenses. You have two options:

1. Store in an environment with constantly moving air of a humidity lower than 60% (considered to be the germination threshold), or
2. keep your camera in the freezer.

You could try bombarding them with UV light, but that's not a cure in any sense... The best thing to use to clean-out a camera lens and body is that 'athlete's foot' spray you can get, from the supermarket. It's predominantly alcohol and oil-based, and contains anti-bacterial compounds that can't hurt, either. Another good idea that people say is not to breathe heavily on your camera lens, prior to cleaning them (old-school style), due to the bacteria and fungal matter in your mouth... I like doing that, though; I've never infected a camera lens yet.

The camera lens is made of various lens elements. If it consisted of only a single simple lens, the image produced is degraded by 7 major defects called aberrations. Additionally the one called a color aberration has two different errors. Aberrations are mitigated by constructing the lens using several lens elements. Each has a different shape (power) and many are made using a high density glass, while others are made from a lighter material. Now some elements are cemented together and some are air-spaced. Let’s talk about the cement. One of the best optical cements is made from the sap of a pine tree called the Canadian Balsam. In recent years, Canadian Balsam cement is being replaced by synthetic resins. Anyway, these cements are organic and thus are food for mildew spores. Most mildew you see today is actually crazing. This is a condition where the cement hardens, becomes too brittle and shatters. You will see this less and less, as the older style cements pass by the wayside.

Nothing you can do to correct; the lens must be disassembled and re-cemented.

...Fungus can be destroyed with the ultimate super-weapon - OZONE !!

.. Ozone done correctly kills bacteria, viruses and is a completely effective sterilizer . .

...Ozone can destroy fungus inside a lens without the need to disassemble it . .

The belief that a lens with fungus can infect others nearby is nonsense. The spores that cause fungus to develop are in the air around us at all times, only "clean rooms" are likely to be free of airborne spores. A lens gets fungal growth because of one thing only: poor storage. ALL lenses in day to day use will have fungus. Within a day or two of being unsealed a brand new lens will have fungus. All we can do is ensure that the conditions necessary to its growth don't occur. Dry air, constantly circulating is the best preventative.

Folks, Mold and mildew spores are everywhere so no escaping. Furthermore, all lenses breathe when focusing and zooming so that's how contamination occurs in the first place. Why do desert dwellers not have this problem or at least have much less problems? B/c the humidity is very low most of the year. Therefore, my recommendation based on this logic, and to make maintenance as easy as possible (most of us don't have time to "nurse" our lenses), is to purchase oversized (relative to the lens/lenses) air tight containers and use a good amount of desiccant to maintain a stable, very low humidity environment. Remember, you need enough desiccant to initially absorb any humidity in the container upon sealing it and then enough to draw moisture out of the lens(es). Ozone is harmful, if not deadly, to life with too much exposure, plus b/c it's a gas, is almost impossible to work with without special equipment. The problem with ozone treatment is getting the gas inside the lens. This will require pumping the lens - moving lens barrel in and out of external housing - to draw ozone into the lens. I don't believe this is feasible since ozone is a gas and will escape unless contained which would require lab equipment IOT avoid exposure. So again I come back to my idea stated at the beginning. LMK if anyone has been successful with that method. Again, the container must be large enough (but not too large) to allow some air circulation which allows the desiccant to work properly. Good luck and share any proven ideas with the rest of us if you run across any. --Mike

I had noticeable growth in my Nikon zoom lense. I did not see any affects on the photos but didn't like the idea so had the lense cleaned. Here in Thailand it cost 75.00 usd. To prevent future problems I spent 60.00 usd on a dry box to store all camera equipment.

The fabric in bag a great place for mold spores to get embedded. . It was suggested when cameras and lenses not in use to put them in an air-tight, transparent, plastic or acrylic case with silica gel. To recap what invites disaster: fungus needs heat, damp and darkness to thrive. recently saw on YouTube - BTW an interesting place for instructions and answers - that you should never store cameras or lenses in camera bags.So dark, moist places surrounded by lower grade of fabric invites disaster

Final answer, disassembly of affected lens and removing fungus provided that the fungus hasnt damaged coatings/glass sooner than later is the best treatment. Best treatment is one you never have to employ. Taking care of your valued equipment from factors that cause damage before they appear is the most prudent. As for fungus, it’s an opportunistic living organism hardwired to survive. It’s everywhere in the environment, waiting for its opportunity. Just stopping one of its requirements will keep it from flourishing. Also, it’s spore can be damaged, and kept from replicating, by the numerous compounds, specific UV rays, and toxic gases. Most of these damage the spore at the cellular level and are quite effective. UV light (254nm) from a modest germicidal bulb at point blank range can render a mold/fungus spore fatally damaged in seconds, but the light source has to fall unmitigated on the organism for a certain time. Also once mold has formed, simply killing it, won’t improve lost optical clarity, that only cleaning can. Best to think of a fungus infected lens damaged beyond repair, and keeping future lenses free from infection thorough prudent anti fungus preventative practices.

Found the answer mentioning leaving the lens exposed to UVs as a way to kill fungii in your lens in the quick Google answers. Unfortunately, glass stops UVC, (the killer ones) making this option not effective. See UV filters for pools for instance, the bulb is contained in a quartz sleeve as a glass one would not permit UVs to do their sterilizing work. For this reason any cheap sunglasses will be able to advertize "Blocking 99% of UV" and manufacturers will sell you a useless piece of cheap glass ruining your nice lens on the premise it will block UVs. Also, while here, storing your lens in an airtight container with dessicant is also not a good idea as it will, as intended, dry your lens to the point of damaging sealants and adhesives