You have just opened your camera case, the one you have not opened since who knows when. You reach in and take out your prized Teliflorist Telephoto 290mm 11.4 and swiftly mount it on your Doeverythingmatic SLR, planning on using it to capture that once in a lifetime shot of a Doublebreasted Yellowbellied Stool Pigeon on your birdfeeder.
“Why can’t I get it to focus clearly?” you ask no one in particular. A quick assessment discloses that there is an obvious growth on the lens surfaces. FUNGUS! If you are very lucky, the fungus will be on an exterior surface. But, in all probability, it will have grown on inner surfaces.
The first and best method to solve this is “Do not let it happen.” Proper storage will, in most cases, prevent fungus. All bets are off if you store your cameras and lenses in a climate that has continuous periods of hot and humid weather.
Storing gear in an airtight container with an ample amount of a good desiccant (silica gel), along with very regular examination to assure that the desiccant is still working, is the best and simplest method. It helps to maintain fairly constant temperatures.
A quick warning: simply putting the gear in a plastic bag that can be sealed is not a good idea. When stored, the gear may have enough moisture in or on it, even though it is not visible, to encourage a growth of fungus.
If the fungus is on an exterior surface, start the cleaning process by using a blower to remove any loose dust. Follow this by using rubbing alcohol, available at any drug store (not denatured alcohol since the agent in it is usually sodium hydroxide, a very corrosive material). Use the alcohol as you would use any other cleaning liquid.
If the lens is coated and the coating is very soft, it is possible that the coating will be removed. This is the choice: leave the fungus and not be able to use the lens or try to remove the fungus and have a usable lens without coating.
You can try a mild abrasive material if the alcohol treatment does not work. Common tooth paste works very well. Use a well dampened cleaning tissue, put a small amount of tooth paste on the tissue, and use a circular motion over the entire surface with minimal pressure. The fungus, if left in place long enough, will actually etch the glass, and only professional polishing may remove the etched mark – and it may very well not.
For fungus on interior surfaces, the task is probably best left to professional servicing. In order to expose the interior surfaces, the lens has to taken apart. Not too many do-it-yourselfers will have either the specialized tools or the expertise to reassemble the lens correctly.
If you really want to try this cleaning I strongly suggest that you attend the next PHSNE Auction. Buy an inexpensive lens that fits one of your cameras and experiment with it. Take several photos of subjects that will be available after the experiment. When the cleaning is completed, take repeat photos and compare them for quality.
Many older lenses will have their elements permanently spaced and this will allow reassembly without the need for collimating the lens. Newer lenses may require adjusting elements to achieve proper focus. This requires considerable knowledge and equipment making it more difficult than the average person can do.