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

Question

Recently I was using an old Pentax 50mm f/2 that had a quite big green spot, and later I was informed that it was a fungus.

A couple of questions raised from this:

1. Why does fungus form inside the lenses? What kind of "food" does it find in a glass element?
2. How does it form? Due to condensation? Due to bad storage?
3. Does it have any impact in the final image? Some scratches in a lens will probably not appear in the image because to they will be very out of focus. Is this also true for fungus?
4. Finally, when a lens is "fungused": How do you get rid of it?

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What to do about mold/fungus in a camera lens?

by Yuttadhammo

I am living in a tropical country where humidity is pretty high. I never thought it would be possible that something could grow inside a lens, so I haven't been so careful with my canon camcorder. Now I see there is a white spore growing on the inside of the camera lens (see photo below). Is there any way, short of finding a camera shop (doubtful there are any in the country that can handle this), to remove this?

The spore is the white dot in the centre (it's opaque), and the dusty patch on the right of the lens is also on the inside, must be the same stuff.

Answer 1

For all the following: YMMV*, caveat emptor, no responsibility taken for advice given, you decide whether to try this at home. It may even work :-). Be aware that damage may already be fatal and/or that fatal (to the lens) damage may occur along the way. Best attitude is to regard the lens as a write-off now, with anything you can gain from it by the methods below being a bonus.

Fungus in a lens will always degrade the image but the amount of degradation may be invisible to mere mortals or may make the lens completely unusable by any standards. Often even a very visually significant lens defect - such as a chip or scratch, will not be instantly obvious in final images to a casual observer. Experts will usually be able to detect almost any defect (or say they can - mere mortals will not be able to tell if they are correct :-) ). Also, lens settings will affect how much a given defect affects a given image.

In some cases the advice given in 1a and 1b below will transform results from generally unacceptable to generally acceptable. In other cases they won't. Only trying it will tell you how good a method will be.

The best advice (but too late :-( ) is to never let it happen. Fungus only grows in moist conditions. Keep your lenses in a well ventilated dry location with desiccant sachets. However -

If it's inside the lens there are two options (apart from disposal). Unfortunately, while either may work, neither is certain to work well.

• 1(a) Shining UV (ultraviolet) light into the lens for an extended period will "discourage" the fungus, how well and how long is uncertain. Simply leaving a lens with iris fully open on a sun facing window ledge in a dry location for weeks to months may produce good results. Cap lens at rear, and tilt so that sun shines into lens during sunnier parts of each day. (Be ware that sun shining directly along the axis of the lens or close to it may focus light onto end cap and melt it - unlikely but check point and degree of focus.) I tried this procedure with an extremely old Minolta 50mm f1:1.4? manual lens and achieved tolerable results. I simply left the lens as above for many months and when I next looked found that mold presence had been very substantially reduced.

1(b) Light from a germicidal (short wavelength) UV lamp may be used in place of sunlight. This sort of light can blind you or damage your eyes permanently if looked at for substantial periods and can cause "arc eye" - painful but usually temporary inflammation of the eye. This does not mean you should not use such lights at all - simply that they need to be used with due respect. These lights are available from many sources for many purposes and can be very low cost.

Note that "black light" UV light is not suitable for this purpose. It is longer wavelength and not very biologically active.

Note also that the short wavelength high energy UV (which is why you are using it) from germicidal UV lamps will also degrade other materials such as some plastics and miscellaneous other material - including, possibly, parts of a plastic lens housing. This depends on material, distance, light energy and exposure time. YMMV but caveat emptor - ie know that you are using a tool with sharp unguarded blades (even though you can't see them) and use with due caution.

All the above may put some people off UV germicidal lamps. If so, that's good. They are a great and useful tool but not suitable for use by careless or unthinking people.

• 2 . Dismantle and clean. If the lens is so degraded that it is unusable and if the method above does not work well enough then the lens must be dismantled. If the lens is otherwise a 'write-off" and you are competent mechanically you may wish to try this yourself. Reassembly of a lens capsule is considered to be an expert task and realignment on reassembly may require arcane knowledge. This is why qualified lens servicing people are still in business and cost money to use.

Fungus often attacks lens surface coatings and may etch the glass itself so the lens may be noticeably or fatally degraded regardless. How much the may/may/may applied in your case is tbd. Some lens cleaning works very well indeed. An aficionado and a good MTR test will probably tell you that something has happened but the results may be very tolerable in practice.

You will find articles on the internet on lens cleaning methods. I read a paper by either Zeiss or Leitz that suggested that cigarette ash makes an excellent fine cleaning compound (!!!).

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• YMMV - Your mileage may vary.

• Caveat emptor - let the buyer beware = you are on your own.

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Added: Member 19602 made this comment - as he has left and comments may too I'm adding it to my answer.

On April 7th 2013, once was member 19602 said:

• I can tell you with absolute certainty that the Leitz recommendation is not a sealed container with desiccant but an area with constant air circulation. I used to be with Leitz Germany.

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Added 2023:

The ability of lenses to pass UV has been questioned.
They do.
How much so will vary, but UV lens treatment is well established.
This diagram shows light transmission for a borosilicate glass - typically used in "float" process sheet glass. Lens glass will vary but enough UV gets where its needed.
In this example:
UVC is almost wholly blocked with even 1mm thick glass.
A significant portion of UVB is passed even by the 8mm glass.
Most of the UVA is passed in all cases.

Image from here which is from this paper

Answer 2

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.

Answer 3

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.

Answer 4

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.

Answer 5

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]

Answer 6

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.

Answer 7

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.

Answer 8

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.

Answer 9

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

Answer 10

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

Answer 11

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

Answer 12

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.

Answer 13

...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 . .

Answer 14

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.

Answer 15

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.

Answer 16

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.