[calicojack]

I have an old Samyang 100-500mm lens that has some fungus growing inside. I've had a local repair guy look at it and his opinion was to just keep using it until it got too bad, then throw it away or dump it at a yard sale. He said it would be ~$100 for the repair tech to just look at it. I tend to agree since it was a cheap lens 20 years ago when I bought it. However, I've heard some discussion that Sun light could kill the fungus. Does anyone have any knowledge of this? Can I just buy a full spectrum plant light (or sun lamp, or ?) and arrange 24 hr/day sunlight shining through the lens and eliminate some or all of the fungus? Would this have any effect at all? Any other ideas? It's rare that I want the 500mm reach and not worth big bucks to repair a cheap lens.
Thanks for any input,
Brian

[stevebrot]

Even if the sun (ultraviolet) lamp killed the fungus, the residual filaments would still remain. Still, it might be worth the try.

Steve

[bobrapp]

I would dump the lense asap. There is a good chance that the spores will infect your other lenses!

from experience

[Wheatfield]

I have an old Samyang 100-500mm lens that has some fungus growing inside. I've had a local repair guy look at it and his opinion was to just keep using it until it got too bad, then throw it away or dump it at a yard sale. He said it would be ~$100 for the repair tech to just look at it. I tend to agree since it was a cheap lens 20 years ago when I bought it. However, I've heard some discussion that Sun light could kill the fungus. Does anyone have any knowledge of this? Can I just buy a full spectrum plant light (or sun lamp, or ?) and arrange 24 hr/day sunlight shining through the lens and eliminate some or all of the fungus? Would this have any effect at all? Any other ideas? It's rare that I want the 500mm reach and not worth big bucks to repair a cheap lens.
Thanks for any input,
Brian

IMHO, any lens with fungus should be thrown in the garbage. If you keep it, you risk infecting every lens you have, if you sell it, you risk infecting every lens of the person you sell it to.
One may say, buyer beware, but I don't like taking advantage of people's lack of education to make a few dollars.

[wildlifephotog]

Or you can clean the lens properly and keep it.
There is a way to save those lenses if the glass has not been etched.

[Wheatfield]

Or you can clean the lens properly and keep it.
There is a way to save those lenses if the glass has not been etched.

Very few lenses are actually worth the effort.
A Samyang isn't one of them.

[wildlifephotog]

Depends on ones financial level.
I like getting nice, repairable lenses cheap.

[UliBär]

Well, i have a K 50/1.2 that had a little infestation of fungus ~1mm diameter, right on the 2nd element ~4mm from the edge. I had this lens for an apple and an egg from the bay and got it professionally CLA'ed for ~70€. This lens is now in like new condition and the image quality is outstanding. The fungus had not left any traces on the lens surface. You may give it a try, if you think the lens is worth it - the K 50/1.2 definitely was!

[Bactman]

I would dump the lense asap. There is a good chance that the spores will infect your other lenses!

from experience

There is a good chance that mold spores are already inside your lenses (as well as everything else). Mold spores are ubiquitous throughout nature - they are everywhere and anywhere. The key to controlling and preventing mold growth is moisture: reduce the ambient moisture level, then any mold spores present will not germinate. The spores need a lot of moisture to initiate germination (more that levels capable of supporting/sustaining hyphal growth).

As for using sunlight to "kill mold" - that may kill it (strong emphasis on may), but what about removing the particulate matter itself? Wouldn't that also potentially impact image quality? I would also be concerned about etching of glass due to hyphal growth on the surface of the glass. This may reduce image quality as well.

[Wheatfield]

Well, i have a K 50/1.2 that had a little infestation of fungus ~1mm diameter, right on the 2nd element ~4mm from the edge. I had this lens for an apple and an egg from the bay and got it professionally CLA'ed for ~70€. This lens is now in like new condition and the image quality is outstanding. The fungus had not left any traces on the lens surface. You may give it a try, if you think the lens is worth it - the K 50/1.2 definitely was!

My concern with fungus is that unless the lens is 100% disassembled and meticulously cleaned with an antifungal, some spores my remain to come back to haunt you.
All it takes is one spore........

For me, with the number of lenses that I own, I won't take the chance on an infected lens. It would have to be a very rare and valuable lens for me to take the chance.

Not all fungi will grow on glass, BTW. The common household molds won't.

[wildlifephotog]

To each his own.
I have never had fungus return or spread in any of my lenses, 75 at last count. None of the bodies have ever seen fungus. Of course I don't use cases for cameras or lenses. They are fungus hotels if not treated.
But again, everyone does what one is comfortable with.

[calicojack]

Very few lenses are actually worth the effort.
A Samyang isn't one of them.

This is what my local repair guy was saying. I must agree that it doesn't make sense to me to spend bigger bucks to clean it than I probably spent to buy it. I will keep it isolated from my more recent lenses and far away from my new(ish) lenses.
I want to thank everyone for their input and saving me the time and money of trying to correct it by shining light on it.
Brian

[richard64]

Not all fungi will grow on glass, BTW. The common household molds won't.

Sure the mould that grows on glass (or rather the cement or coatings on the glass) is not the same that grows on bread. But ask yourself why your lunchtime sandwich is not covered with mould. The reason is that the spores will not grow unless there are the right conditions, and they are given a chance to grow. It is much more important to prevent the conditions (not let your lenses sit for a long time in damp conditions), and it is far easier to do that than it is to eradicate all spores.

As you say, it just takes one spore, but if that spore cannot germinate then it is dust.

Richard

See if you can take it apart. You haven't really got anything to lose,a t least you'll get to see how a lens is put together.

[calicojack]

See if you can take it apart. You haven't really got anything to lose,a t least you'll get to see how a lens is put together.

I might try this. You're quite right, nothing much to lose.
Brian