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Lens fungus question

Suhas Kulkarni , Feb 12, 2006; 07:36 p.m.


My canon 100/2.8 USM macro lens caught fungus, which is quite severe. The lens elements are not affected yet but the fungus has grown totally inside.

I asked local shop (Melbourne - Australia) and they said that I have to send the lens for inspection which will cost me $44 for inspection alone! I asked what is estimated cost for repair - they gave no figure at all. I am afraid if I send the lens for inspection and if they quote something like $300 / $350 for lens cleaning then I will not be interested in getting it done and so my $44 will be lost and my lens will still remain in bad condition.

So, just want to ask - what is estimate to clean lens fungus? Can I just stop fungus growth and use the lens as it is (it does not seem to affect picture quality in normal distances)? If so what is the way to stop the fungus growth?

Regards, Suhas


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Ryan Disney , Feb 12, 2006; 07:51 p.m.

I might be perpetuating a rumor, but I've heard that if you leave the lens in the direct sun for a while it will dry out and kill the fungus. Being a biologist, it seems plausible. It should keep it from getting worse, and will probably make it a bit clearer.

I could be completely wrong, as I've never had to try it.

Joshua Szulecki , Feb 12, 2006; 08:02 p.m.

Ryan, I think I have heard that leaving a lens out in the hot sun can damage the lens by causing libricants to leave their normal "homes" and get into places they don't belong. If one were to try this, and I don't personally recommend it, I would suggest doing it on a cold day, and make sure you take the UV filter off (if there is one) because it is likely that the UV is what would be killing the fungus. Does UV kill fungus? I know it is used against bacteria...

Bob Atkins , Feb 12, 2006; 08:11 p.m.

Even if you could kill it, the dead fungus would still be on the elements and needs to be cleaned off. If you don't kill it it will etch the coatings and eventually etch the glass.

I presume they don't want to estimate until they know just how bad the damage is. In the worst case, elements may need to be replaced, in the best case the lens still has to be taken completely apart, cleaned and reassembled, which probably takes at least a couple of hours. What does 2 hours of skilled labor cost? $100?

Larry McGarity , Feb 12, 2006; 08:14 p.m.

The only way to get rid of fungus is to dismantle the lens for cleaning. It won't go away by itself and it is serious. From the way you describe it is in an advanced state and that is not good. You need to act quickly if you value the lens. If you don't you might as well throw it in the trash. Personally I would pony up the $44 for the inspection tomorrow morning but to each their own.

If you catch fungus early the elements can be cleaned. And its also possible to recoat an element in some cases. But the longer you wait the more the damage. Eventually the fungal waste products will eat through the coating and etch into the glass. Once that happens that element is ruined. There is no cure. I suppose you could pay to have the element or elements replaced, but I suspect that would be an expensive proposition.

To prevent fungus you should not store cameras or lenses in humid conditions. Air conditioned environments are best.

I have no idea of the cost to clean a lens in Australia.

Professor K. , Feb 12, 2006; 10:41 p.m.

The local and long-gone camera store owner told me that leaving a lens outdoors so that all the insides got exposed to direct sunlight would kill fungus. I did a google (or something) search on this quite some time ago and found some contrary views. Specifically: [1] Ultraviolet will kill the fungus, but not the spores, so it may come back; [2] Glass will absorb enough UV that you may not kill the fungus anyway. Sorry but I no longer have a source for these items. Conventional wisdom is that the fungus will spread - keep that lens away from the others! Perhaps a biologist can give us some defintive insight here?

Larry McGarity , Feb 12, 2006; 11:01 p.m.

"Conventional wisdom is that the fungus will spread - keep that lens away from the others! Perhaps a biologist can give us some defintive insight here." Conventional wisdom is wrong. Fungal spores are everywhere, but it takes moisture to activate them. Fungus contamination is caused by storing equipment in excessively humid environments pure and simple.

Suhas Kulkarni , Feb 12, 2006; 11:17 p.m.

Thanks all for the replies.

Right now the lens is kept in direct sunlight. But soon I plan to send it for cleaning assuming they quote some reasonable amount for repair. I will wait for the quotation.

Actually I rarely go to 1:1 magnification, normally 1:2 is enough for me. Also on 1.6x crop DSLR I can get good working distance even with 50 mm lens. Hence I was actually thinking that if the cost of cleaning is too much I would just buy a brand new 50 mm macro instead ..... Of course I am aware that 50mm macro is non-usm, so-so build quality, difficult to focus etc. But I still get a *new* lens compared to 6 year old lens that I currently have (and also there is no guarantee from the shop about completely fungus-free lens after cleaning)

Kelly Flanigan , Feb 12, 2006; 11:39 p.m.

My canon 100/2.8 USM macro lens caught fungus, which is quite severe. The lens elements are not affected yet but the fungus has grown totally inside.

I dont understand this comment. The lenses elements are not effected; but the rest of the lens is. Normally one sees fungus first on the optics. I not really sure if I have seen fungus much on aluminum lens mounts at all. Getting fungus is common on leather cases. In early stages fungus just drops the image contast, it maybe cleaned off. In later stages the coating gets removed in patches. The byproducts of fungus are acids that eat ie divot/pothole the glass surface. In practice alot of folks greatly worry about small lens defects that cannot be measured. In survey equipment one just cleans the dirty lens and bores, and one moves on with life. Photographers seem to be more emotional.

Suhas Kulkarni , Feb 12, 2006; 11:44 p.m.

I mean the fungus is visible but the glass elements seem to be intact, i.e. there is no visible mark / dent on the glass when I see through. Only the fungus web is visible.

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