Lens fungus questions

craig_d

1. I've actually never seen fungus in a lens... until, possibly, today. Is this fungus, or just crud? (100% crop of front element, taken from another lens, with a light source shining through.)



Whether it's fungus or not, I have a couple of other questions on the subject:

2. If a lens with fungus is stored with other lenses, is the fungus likely to spread to them? (Assume lens caps are kept on both ends, but most lenses probably aren't airtight in any case.)

3. Should a lens with fungus not be used on a camera? Might the fungus spread to the mirror, prism, or sensor, or might the camera become a carrier for other lenses to get infected?

Fortunately this isn't an expensive lens; it's an old Nikkor AI-S that I picked up very cheaply just recently. I thought, on visually inspecting it, that this was just dust, but my lens pen couldn't clean it off, and then I looked closer... if it is fungus, I suppose I should throw out that lens pen too.

Thanks for any information anyone can provide.

Bear Dale

Keep this AWAY from your other gear.....very very far away. Don't infect all your gear with fungus spores.

ziggy53

"Lens fungus" is a broad classification of plants and it usually takes the form of dots or threads. This does look like the second variety.

Since a fungus usually spreads through emitting "spores" into the air, it's possible that some spores could escape the lens body, but it's more likely that similar spores are already present in the air in greater quantities, so just using a lens and then improper storage can cause the problem.

Some lens coatings seem to host the fungi and some lubricants are potential hosts too.

High concentrations of moisture are normally the common denominator and it can be from exposure to rain or mist, or just very high humidity, and then improper storage, trapping the moisture and creating an environment favorable to growth.

If it's not a valuable lens I think just retire it or even toss it. Dismantling and simple element cleaning will temporarily cure the lens elements, unless the fungus has attacked the coating itself. The fungus will usually hide in the parts most difficult to clean so a reinfection is likely. Some folks use regular UV exposure to slow or stop reinfection, and that works in some cases. Dry storage is still the best strategy.

Rereading your description it sounds like the front coating was affected? If you don't see an internal problem then you've probably got most of the plant removed and some of the fungus by-product etched the front coating. I suggest a mild ammonia* solution to clean the surface as completely as possible. In most lighting you might not even detect a problem in the images taken with this lens. I'll bet contra lighting will create reduced contrast, much like lens flare.

*After reading some reports of ammonia removing the lens coatings on old lenses I now suggest just using commercial lens cleaners instead.

craig_d

Thanks for the info.

I think the growth is at least partially on the inside of the front element, but it's hard to be sure. I can't tell if there's anything deeper inside.

I took a few shots with the lens before realizing that the crud might not just be dirt. The images came out fine, but I'd rather stay away from fungus-infected lenses, so I'll probably just toss the lens and buy a replacement from a reputable source. It's a Nikkor 135mm f/2.8 AI-S -- pretty easy to come by, and inexpensive, on the used market.

ziggy53

Researching a bit more about using ammonia on very old lenses it appears that some folks think that ammonia will actually remove some of the early lens coatings. I'm not sure if that's true or not, but I suggest erring on the side of caution. I'll amend my reply above.