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Jonathan
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 18, 2005 - 03:44 pm: | 
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I've periodically irradiated all my cameras and lenses with UV light to try and avoid fungus. However, in at least one case, the fungus has returned. Well at least I think it was fungus, I cleaned it off anyway...
As you can see, I'm not convinced that the UV actually does anything. I can think of many reasons why it wouldn't be a complete solution, anyway.
Has it ever been established whether UV treatment works to prevent fungus growing in lenses? Do many people use this method?
The light I have is a T-UV germicidal bulb (out of an eprom eraser). I called a lamp supplier and asked about it, and the man seemed to think it would wipe out all life instantly.
I feel a bit silly putting my cameras in a biscuit tin with a light bulb, so I'd appreciate any justification for or against. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 18, 2005 - 07:35 pm: |
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Jonathan
I have always thought that the old dodge of airing lenses and cameras in sunlight was more to do with getting the equipment warm,than irradiating with UV.I keep all my equipment in sealed containers with desiccant cartridges.The cupboards are also fitted with rack heaters,but then I live in a very old stone property with all the attendant problems.
UV sterilisers obviously work for water supplies and I suppose fungus spores also.A word on fungus reappearance;remember that having spent hours cleaning the glass you must then completely strip the mount,to remove all traces of fungus spores.The stripping and cleaning should not be done at the same bench that the final clean and rebuild is carried out on.Simple hygiene precautions can save repeated strip-downs.
I try and provide an environment that will not support fungal growth.However like your UV, I do not know if it is working because it is preventing spores that are present from growing,or the apparent success is because no fungus is actually present. |
rick oleson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 09:56 am: |
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One thing that may be an issue is whether the UV light actually penetrates the glass to get to where the fungus is; lenses are transparent in the visible range, but not necessarily into the UV and IR.
I have never had fungus occur in a lens in my possession; the only time I have ever seen it has been in other peoples' equipment. I think in the sort of temperate climate where I live, natural ventilation (ideally with air conditioning in the summer) is a good way to discourage it. I would avoid keeping lenses sealed up or in cases, unless you're good about maintaining dessicant packs.... but I don't have personal experience with both promoting and then stopping fungal growth to speak with authority on the subject. |
Mike Kovacs
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 11:47 am: |
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Glass is very efficient at filtering UV, particularly the shorter wavelength stuff. In the lab, my UV-visible spectrophotometer has QUARTZ optics where glass would normally be used. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 12:03 pm: |
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Rick,
Agree completely;natural ventilation and a temperate climate are the best way of keeping optics in good condition.My dessicant packs are very large industrial cartridges,produced for military use and have more than adequate active life before needing regeneration.
Like you, I have never had fungus appear on a lens in my possession.I have purchased examples with fungus present and then rigorously cleaned the item in question.Maybe I am lucky but it has never returned,However I do draw the line and do not purchase heavily contaminated optics.
That fungus can grow rapidly in the right conditions is without doubt.In my home city there is a shop that sells ex mil and ex BBC broadcast equipment and sound level measuring equipment-another interest.The shop is situated in the railway arches beneath the railway station,musty and damp!Just over a year ago there appeared a load of Canon FD stuff,including 50mm and 100mm macro lenses.The proprietor wanted a fortune for it,so it has been just sitting in a glass counter.The lenses are now festooned with fungus,where filters are attached the outer surface of front elements are covered,the prism/mirror/viewfinder of the A1 and AE1 are so covered that you can hardly see anything on the screens.The price being asked is still more than the kit is worth-a shame because it now looks terrible.
Trouble is owner has found a recent magazine article that states fungus does not etch the coating/glass and can be just wiped off.I was under the impression that a long term fungal attack would etch the glass.Am I right or wrong in this?
Glenn |
Roger Provins
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 02:48 pm: |
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I am sure you are right Glenn. Can't imagine why the author of the magazine article should think not as even in my limited experience I've cleaned off fungus many times only to find that the glass was permanently damaged.
Roger |
David
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 03:15 pm: |
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If glass is very efficient at filtering UV, why to lots of photographers keep UV filters on their lenses? |
Jonathan
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 03:17 pm: |
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It's sad to see valuable stuff go to waste.
I just found out that TUV lamps have most of their output at 253.7nm, which is UV-C. Would lens glasses transmit anything at that wavelength? I'd always imagined a bit would get through.
Glenn, your rack heaters sound interesting. I've often wanted such a thing, but always been put off by an imaginary fire risk. How do they work? Did you make them or buy them? |
paul ron
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 05:03 pm: |
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I doubt UV will do anything either. i have an old EPROM burner that has a powerfull UV light in it that erased these programmable chips. I put a fungus eaten lens under it and I don't see any difference. Perhaps to use the UV light to keep fungus from starting? Maybe doing a UV treatment before storing the equipment? I know these bulbs are used in some sterilizers. Whadaya think? |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 05:53 pm: |
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Roger,
Thanks for the confirmation on the etching properties of fungus.What surprised me about the article was the fact that the author is a respected expert on old cameras and a regular contributor.I had seen the article before as I subscribe to the mag,but was taken aback when the shop owner brandished it in my face saying 'it's only a bit of dirt'.Some dirt!
Jonathan,
The first one I made myself,but only because I had some suitable materials.When I started work we had a tube muffle furnace and because we always ran it at max temperature, the elements kept failing-these were just constan resistance wire wound round the silica tube.They were expensive to replace but my boss was a practical person as I am ,so we decided to wind our own elements.I got plenty of practice!Years later I became boss and inherited this great roll of resistance wire which had been redundant for years.It was quite easy to wind up some elements on heat proof board.
I soon discovered that RS Components sold a nice little thermostatically controlled unit,come in various wattages.Basically you decide the temperature you want to maintain in the cabinet-find your average low temperature-pick the unit that matches your temperature range-then plug in the mains and forget.You can get similar results with light bulbs,but the proper item has no fire risk and will not overheat under any circumstance-thermostat and thermal cutout.
Glenn. |
rick
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 06:11 pm: |
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I'll add my 2 cents on the etching thing... I've seen grooves etched by fungus so deep that you could feel them as you dragged your fingernail across the lens surface. Even in a lens that can be fairly well recovered, I have often seen marks that could be detected on very close inspection after the fungus was removed. The author of that magazine article obviously doesn't know what he's talking about... he may have encountered a few lenses that could still be cleaned, and assumed it doesn't get any worse.
As my father once told me: "Indians always walk single file - I saw one once."
rick : ) = |
Lee Crump
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 19, 2005 - 10:13 pm: |
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Is it possible that the fungus is eating the optical coatings on the glass instead of the glass itself? |
Jonathan
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 20, 2005 - 12:08 am: |
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A lot of visible fungus damage would be just to the coating, but in bad cases you can definitely feel the grooves, and the coatings are nanometers thin. |
rick oleson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 20, 2005 - 07:57 am: |
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yeah, it's well into the glass. it might be that the coatings help it get started though ... offhand i can't recall seeing the problem in any uncoated lenses, and that seems kind of odd given the number of them that i've handled.
: ) = |
Henry
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 20, 2005 - 01:02 pm: |
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All fungi are not created equal. Some harm glass, some don't. I've cleaned heavily covered glass that wiped off easily leaving a pristine lens. And I've seen very light fungus leave a deep groove.
If one does know fungi (which I certainly don't) guess they could tell the difference. But for the rest of us it's a crap shoot.
Henry |
Roger Provins
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 20, 2005 - 02:07 pm: |
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Which gives us with an interesting question to put to a specialist on fungi, not a camera person, just what is this stuff? Anyone know such an expert?
Roger |
Ezio
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 23, 2005 - 05:08 am: |
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AFAIK (and still waiting for a fungi expert to come forward), these things live and "feed" on the coating - that is, they would not attach an uncoated lens because the glass itself does not provide an environment they can survive and grow into. Fungi per se do not attack glass - the etching (which I would unfortunately confirm can be pretty deep) is rather caused by the chemical byproducts of their "feeding" process - their shit if you wish. Here again, AFAIK. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 23, 2005 - 10:25 am: |
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From my observations of the Canon equipment mentioned above,I can clearly state that the fungus has covered uncoated filters and the prisms of the cameras in question.What I cannot state is if the fungi will just wipe off the uncoated glass.My suspicion is that these organisms are more akin to lichens,when it comes to their attachment/growing habits.Using this I can come up will a chemical/boundary bond that explains why the fungi will attach to coating and then continue to etch into the glass;ie a coating is needed for a permanent bond to start forming,otherwise the fungi just spreads-looking to put down 'roots' on a suitable surface.
As for expert,I have asked my university prof Brother to mention it to his colleagues.However I suspect they are a bit busy organising the new term,to give an immediate answer. |
Ezio
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 25, 2005 - 08:33 am: |
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If the "thing" has grown to cover uncoated filters and the prism, then I would suggest it is mold. I seem to understand that mold is also a fungus of sort (or the byproduct of the presence of a fungus, whatever), but cleary it is not the same as the fungi that attack lenses. I had only one personal experience with mold. I was given a Super Ikonta A that was nearly completely covered with greenish mold - metal parts, leatherette, glass, everything. Fortunately it was possible to remove all of this stuff without leaving any permanent scar, but I cannot guarantee that this would always be the case. |
Conrad
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, September 04, 2005 - 10:40 pm: |
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I've had deposits that were probably fungus or mold that cleaned right off with no damage whatsoever. I've also seen fungus leave deep pits, lines, and haze, that completely destroyed the lens. Here's the interesting bit- a high percentage of the fungus I've seen is on the inside surface of the rear group, with nothing on the nearby front group. My guess is the glass types commonly found in that rear location, are like candy to some fungus, and are very prone to being deeply pitted and grooved. I don't know if it's the crown or flint or something else. I think Japanese cameras suffer more than others, possibly because the assembly areas weren't air conditioned back in the old days, and the climate is as humid as can be during much of the year. Prime example- many Mamiya TLR lenses will have fungus damaged rear groups, equally bad on both viewing and taking, but no other damage. |
Jonathan
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 05, 2005 - 02:08 am: |
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This brings to mind a thought I've had. Would the cavities inside the lens be essentially isolated or open to the atmosphere, over a period of decades?
Obviously some have better ventilation than others. I imagine the diaphragm cavity would equalise with the surrounding atmosphere fairly quickly, but how about a screwed together group? A pretty tight seal, but we're talking years and years.
I have at times held a lens below a freezer door to catch the super-dry air which falls out, wondering if it was superstitious. I've also wondered about filling with dry nitrogen. (Might that have the wrong refractive index??) |
