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Old Apr 3, 2009, 5:14 PM   #1
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Hi I am from Bulgaria.
I have Sony A200. In Ebay I found Tokina AF SD 70-210 mm, 1:4-5.6. The seller described that the lens have fungus. My question is How can I clean, purge or brush the fungus from a lens?
Thank you for your opinions.
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Old Apr 3, 2009, 5:27 PM   #2
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The simple way is to expose it to sunlight in a dry environment.

But while that will kill the fungus, it won't repair any damage the fungus might have caused to the lens coatings.
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Old Apr 3, 2009, 5:57 PM   #3
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And what is the purpose or fumction of lens coating? Is lens coating important for the image quality?
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Old Apr 3, 2009, 6:18 PM   #4
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The best way is to send the lens to a reputable camera shop. TCav's suggestion works partially. The fungus may die when exposed to sun light, meaning it won't continue to spread further. However, it will not disappear from the lens because it's trapped between the glass elements. The only way is to take the lens apart and have each element individually cleaned. My suggestion? Unless we are talking about a very expensive lens here, it is not worth it spending the $$$. Chances are the coating will be permanently damaged and once taking apart and put back together again, the lens will never AF properly.
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Old Apr 3, 2009, 6:23 PM   #5
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Ben_Bulgaria wrote:
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And what is the purpose or fumction of lens coating? Is lens coating important for the image quality?
Absolutely. The coating is probably the most important thing besides the quality of the glass and assembly precision. Poor coating will result in over exposed images, poor color, ghosting, reflection caused by light rays as they travel through the elements until they reach the sensor, and the list goes on and on. That's why it is recommended that photographers use multi-coated filters.
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Old Apr 3, 2009, 6:59 PM   #6
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Tullio wrote:
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... That's why it is recommended that photographers use multi-coated filters.
But UV filters block the UV light that kills fungus, or at least, keeps it from growing. So a UV filter can actually create an environment where fungus can flourish.
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Old Apr 3, 2009, 9:24 PM   #7
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UV does kill fungus. Sun is a good source, as are black lights ot "grow" lights used for plants. The problem is it won't kill spores. As soon as conditions exist that support fungal growth, it will come back.

Fungus destroys coatings, and creates acid that can etch glass. If the lens can be replaced economically, that would be the best choice.

The best thing is to avoid fungus to begin with. Keep lenses in dry conditions. Desiccant bags are good. I use them in a sealed Pelican case. An ounce of prevention.....

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Old Apr 4, 2009, 11:50 AM   #8
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TCav wrote:
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But UV filters block the UV light that kills fungus, or at least, keeps it from growing. So a UV filter can actually create an environment where fungus can flourish.
Normal exposure to sun rays from regular use will not kill fungus. One would have to leave the lens exposed to the rays for quite some time in order to kill them. The killing process is a combination of the UV light present in the sun ray and high temperature. Thus, the exposure to sun rays that a lens gets from normal use is really not enough to kill any fungus. One of the primary reasons why filters can contribute to fungus growth is condensation that can build between the filter and the lens glass in certain environment conditions. Eventually, the condensation will find its way through the glass and get trapped, causing fungus to grow. I haven't heard of fungus growing on lenses that are frequently used because there is not enough time for the condensation to penetrate the glass elements even if the lens is not kept in absolutely dry conditions. Usually, fungus occur on lenses that have been stored for very long periods of time in contact with humidity. Many lenses sold on eBay by sellers who sell items from Estates and/or storage places they buy, contain fungus because they have been stored in non-ideal conditions for years.
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Old Apr 6, 2009, 8:17 PM   #9
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I supposed I 've cleaned about 40+ lenses with fungus. The success depends on how long the fungus has been there.

If it's been there too long, yes, it will etch the coatings and sometimes the glass. I'd say that I have a success rate of around 75% for elliminating the fungus without damage to coatings or glass.

Usually, if the fungus has a small number of thin tendrils across one glass element surface, then it will probably clean without damage. On the other hand, if multiple elements or surfaces have fungus, this is often an indication that the fungus has had time to spread, indicating a longer time in the lens.

If there is a small spot of quite dense looking fungus, with quite a small patch of surrounding fungus tendrils, this will almost certainly have damaged the coating/glass. I'd steer clear of those.
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