Removing fungus from lens?

[Don Simon]

Hi all, those of you who have read some of my previous posts may know that collecting Pentax cameras and lenses is an interest (i.e. scary obsession) of mine. Well, I spotted a 50mm f1.7 lens (PK mount) on Ebay and immediately went for it. Of course buying on Ebay is a bit like sticking your arm in a barrel full of snakes in search of gold at the bottom (weird analogy I know) and this time I got bit. The lens arrived and the seller left me good feedback, however the lens appears to have a significant amount of fungus on the inside of the elements. Since the lens cost me £10 including delivery I won't bother arguing with the seller, however I am prepared to try taking the lens apart in order to clean it. Unfortunately it doesn't seem to be that simple; the mounting ring on the back of the lens is screwed on but the screws will not budge (I've chewed up two screwdrivers trying) so I can't seem to get inside the thing. Essentially what I'm wondering is whether anyone knows anything specific about cleaning lenses of this mount, or whether (a long shot here) there's some kind of miracle cure for cleaning fungus from inside lenses without disassembling them?

Thanks in advance for any advice you can give!

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[PlasticSpanner]

Is the fungus on the front elements? If so and the focuser has a rubber "band" grip then try peeling this back and there may be a couple of screws under that (Just going of Practika B-Mount lenses)


Take care to mark the front elements position first and count the number of turns to remove it otherwise you'll screw up the distance rings!

[Mitica100]

Hi all, those of you who have read some of my previous posts may know that collecting Pentax cameras and lenses is an interest (i.e. scary obsession) of mine. Well, I spotted a 50mm f1.7 lens (PK mount) on Ebay and immediately went for it. Of course buying on Ebay is a bit like sticking your arm in a barrel full of snakes in search of gold at the bottom (weird analogy I know) and this time I got bit. The lens arrived and the seller left me good feedback, however the lens appears to have a significant amount of fungus on the inside of the elements. Since the lens cost me £10 including delivery I won't bother arguing with the seller, however I am prepared to try taking the lens apart in order to clean it. Unfortunately it doesn't seem to be that simple; the mounting ring on the back of the lens is screwed on but the screws will not budge (I've chewed up two screwdrivers trying) so I can't seem to get inside the thing. Essentially what I'm wondering is whether anyone knows anything specific about cleaning lenses of this mount, or whether (a long shot here) there's some kind of miracle cure for cleaning fungus from inside lenses without disassembling them?

Thanks in advance for any advice you can give!

Try to leave the lens in full sun, facing the sun as much as possible.

Regarding your chewed up screwdrivers, do you have a good all-sizes set? You'll need that, otherwise the 'chewing' occur. Always fit the screwdriver to the size of the screw, not any smaller or wider, apply constant pressure while unscrewing and do not tilt the screwdrivers, keep them at strictly 90 degree against the screws.

[Don Simon]

Thanks guys, I'll try the sun thing tomorrow (though it being October and this being England my hopes aren't too high ). I did try removing the grip ring on the focuser but there were no screws underneath. As for the screwdrivers, I did find one that fit perfectly, and still the screws won't budge. At all. Which is odd considering there's absolutely no signs of rust or anything else which could prevent the screws from turning. Anyway thanks again for the suggestions; I'll let you know how I get on.

One more thing (I love doing my Columbo impression)... I don't suppose sticking the lens in a box with a whole load of silica gel would do anything? I'm guessing it's not just dryness but also light that's required?

[PlasticSpanner]

Any fungus will thrive in dark, damp, cool conditions so you need the opposite to kill it i.e bright, dry and warm!

[PlasticSpanner]

Or turn it into a small flower pot!


Can't remember who's idea this was but it was on here some time ago and sounds rather cool!

[Don Simon]

Or turn it into a small flower pot!

With a 50mm?! I'd better go find some very small flowers or maybe a cactus... thanks for the suggestion!

[Mitica100]

One more thing (I love doing my Columbo impression)... I don't suppose sticking the lens in a box with a whole load of silica gel would do anything? I'm guessing it's not just dryness but also light that's required?

It won't hurt the lens but I doubt it will eradicate the fungus.

If you can get access to the exposed lens, a few drops of a 50/50 solution of alcohol and white vinegar on a piece of lens (microfiber) tissue will do some good. Rub veeeeery gently the surface affected and then dry it with another piece. I heard that ammonia also works although I never tried it.

If the lens is not coming apart where it should (at the screws), did you try removing the retaining ring (inside the lens)? Are there any slots for spanner wrenches? If not, you can get a circular piece of sticky rubber and glue it on a round piece of wood. Try to remove the ring by applying some pressure and twisting at the same time.

BTW, can you post a picture of it, especially with the parts that show where the screws are and also of the front? That'd help.