Fungus question

Insp Gadget

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Aug 23, 2009
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Fredericton, NB, Canada
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My wife is looking at buying a lens on Ebay. The owner states that there is a small spot of fungus inside the lens but it won't affect the photos. Can someone explain this subject to me? How does fungus get inside of a lens? Does it get worse over time? Does it affect the photos? Would you buy a lens that has fnugus inside of it?
fungus usually is a result of moisture, and yes it can get worse. I would pass; however, they can be cleaned but then you would need to include the cost of cleaning with the total to help decide if it is worth the purchase.

The lens was in an environment that encouraged fungus spores to grow: high humidity, spores present and food. Fungus spores are everywhere so all you need is the moisture (high relative humidity) and food. The food is organic dust -- a classic food source is organic fabric camera bags.

If the fungus is very minor it will have a negligible effect on the photos, just as a little dust inside a lens is no big deal. As the fungus increases in size it of course shows up more in the photos, primarily as a loss of contrast. If it's really bad the lens becomes unusable.

Remove the moisture and the fungus stops growing, but fungus spores are everywhere so....

The fungus itself can be cleaned from the lens however if it's on internal surfaces the lens must be taken apart -- big ($$$) job with a modern zoom lens. Cleaning the fungus however will not remove damage caused by the fungus. As the fungus grows it excretes acids that etch the lens coating and even the glass itself. This damage is permanent and if it's big enough the lens is compromised.

I would not buy a lens with fungus inside it. Fungus inside a lens dramatically devalues a lens.
I agree. I will not buy a lens with fungus unless the lens is GREAT lens and cost a lot less than others.

I bought a lens on ebay before and I noticed the lens had some fungus on the front lens element. And of course, it did not affect the photos. In other words, I could not tell the photo was taken with a lens with fungus.

Since the seller did not mentioned the fungus and said the glass was clean, so he gave me full refund of the lens and all the shipping cost (to me and back to the seller).

From what I read on the net, normal UV light should kill the fungus so I suspect the lens was not being use for a long time and stored it in a dark place.
Hitting the lens with sterilising UV and keeping it in a perfectly dry environment will keep it from getting worse, however the only way to get rid of it is cleaning.

It's worth noting that fungus can etch through the sensitive coatings on the lenses. Also often it may not be visible in the photo, but it results in a lens that would look less sharp if compared to a pristine condition lens.

I have bought one before. I bought it at a huge discount since it essentially cost me $150 to get the lens fixed.

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