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Preventing further deterioration in lenses (possibly fungus, definitely separation)


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I have a couple of Contaflex Super Bs with (I think) all the lenses they could

have - 35, 80 and 115mm as well as the 50mm.

 

The 80mm is showing some signs of what, I think, is separation of elements - it

looks like an oil-slick is spreading in from the outside of the lens. Is there

anything I should to to stop or slow down this process?

 

The 115mm has curious white spots on the inside of the barrel (well, it's a cone

really) which I suspect might be fungus. There does not seem to be any on the

glass itself. They are all kept in dry conditions now but have been in various

horrible flats in the past which were probably damp. If this is fungus, is there

anything I should do to nuke it? I'm guessing it is not growing now, at least,

as it's all too dry.

 

I don't want to do anything heroic, as I don't use these much, but I'd like to

make sure they stay in as good condition as reasonably possible.

 

Thanks.

 

--tim

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The 80mm problem sure sounds like separation. Keeping the temperature stable is all I can suggest. Cheapest solution is probably replacement.

 

On the 115mm, perhaps you're seeing the ground edge of an element, perhaps the black paint is separating from it.

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You describe two possible problems: Separation of of elements and white spots which may have radial patterns. Separation of elements produces characteristic rings or curved contour lines. In this case the separated elements will produce optical distortion and can only be fixed by removal of the elements and re-heating the glass to melt the optical adhesive. Not an easy process normally but it can be done, especially when the lens is old and used the old balsam adhesives.

 

Regarding the whitish areas - Two processes can occur on old lenses: Devitrification, which is very slow and seen primarily as radial growth and white cystalline areas that may be confused with fungus growth. Second is actual fungus or mold. Your lens would be too young to have devitrification so it's likely mold.

 

The problem with mold growth on optical glass is the fact that in the process of growing the mold leaches carbonates from the glass surface which then appear as white crystalline areas. Removal of the actual mold doesn't restore the glass surface as a result and the damage cannot be repaired without re-polishing the lens.

 

That being said, if it hasn't gone too far the damage is often not sufficient to seriously degrade the image.The research papers I've seen show the mold doesn't actually use the glass for nutrients but the glass is damaged by the metabolic byproducts of the mold growth.

 

John's advice is good. Temperature and humidity are the main causes of mold growth on lenses. This has been a problem with optics for a hundred years, not just old vintage cameras.

 

Any means of sterilizing a multi-element lens such as ethylene oxide, high temperature, or UV exposure, although they may kill the existing mold, don't prevent new growth nor do they restore the optical surface. Many just make things worse.

 

Several manufacturers including Leitz produced tropical lenses and lens containers which were primarily intended to keep the lens dry. The best thing to do is to keep cameras in plastic bags with packets of silica gel.

 

Also, BTW, the molds that have been isolated and identified are fairly common in the environment. It isn't likely that one moldy lens will contaminate others since the spores are already present everywhere.

 

David

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Set the lens out in the sun to kill any fungus. I try to set all of my lenses out for at least an hour once a year around the winter solstice. The low angle of the sun makes it easy to align the lenses to point straight at it, and any other time of the year I'm afraid the hot Texas sun would cause other damage. Even with this minimal intensity, I've still burned little spots in the table! Be sure to remove the UV filter first.
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Actually, my scientific specialty field is radiation-induced DNA damage and cell death. So, I can state that setting your lenses out in the sun will not have any noticeable effect on the growth of mold on the internal optics (or the external for that matter). Exposure to sun may work well on mildew and molds in other things like fabrics but it is not due to any significant germicidal effect, but rather heating and drying effects. These are not applicable to lenses, of course. For one thing, normal lenses don't transmit light at 254nm or below, unless you are using very costly quartz or fluorite glass, and the sun's intensity at those wavelengths is not sufficiently great... plus a long list of other reasons.

 

In the filed of tissue and cell culture, where I spent most of my life, mold is the most serious environmental contaminant and strong UV lamps with outputs at 254nm are at the very best only marginally effective when it comes to surfaces, and never effective when it comes to optics.

 

Exposure of lenses to the sun to kill mold is simply a myth.

 

David

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Tim, your white spots on the edges of the element are probably separating paint, often called Schneideritis because many Schneider LF lenses develop the problem. This is purely cosmetic and nothing can be done about it.

 

Your "oil slick" is due to cement failure and with modern lenses cemented with UV-curing adhesives nothing can be done about it.

 

David, I won't disagree with you about killing fungus spores, but the glass in lenses does pass enough UV to cure cement and bleach color centers created by radiation damage.

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Dan,

 

The UV used to cure optical adhesives is in the long wavelength region. These adhesives are cured by both long UV and visible light. So the curing process goes ahead through a molecular mechanism that is quite different from that of UV germicidal effects and optical transmission is not a problem with normal lens glass. I have used such adhesives when designing optical systems in the past and they work very well and fast (except when you need to reverse the process when something goes wrong).

 

In order for the UV energy to be absorbed by molecular bonds in biomolecules, like those in mold, and cause damage and death, the wavelength needs to be shorter than those used for curing adhesives, usually shorter than 350nm. Transmission of most commonly encountered optical glass drops precipitously around 300nm even in those filters that are designed to specifically pass UV. Pure silica glass (often called "quartz glass") and to a lesser degree some borosilicate glasses can have up to 90% transmission in the 160-300nm range which would be the kind of UV needs to kill "germs". However, these are very expensive optics.

 

We must remember that "UV" is often not a sufficiently precise term since it refers to a broad spectrum on the very upper edge and above the visible light spectrum. For convenience it is ofter divided into UVA, B, etc. because biological effects, e.g. sunburn vs killing bacteria and induction of DNA mutations, are conveniently described by this notation.

 

In the end, exposure to sunlight will only give you a warm lens, not a sterile one.

 

I hope I haven't been strident and offended anyone. If I'm wrong, please let me know.

 

Ciao.

 

David

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Your "oil slick" is definitely separation. Zeiss experimented with various synthetic adhesives during this time period. They are difficult to repair and heat will not enable a repair tech to separate the elements for cementing like with Canada Balsam adhesive.

 

You could check the archives for Rick Oleson's "oil trick". It has worked very well on a CZ Sonnar lens I have with the problem and cost me nothing to try.

 

As for UV, DNA damage is not the only cause of cell death. Have you considered free radicals David? The fungii within lens elements are normally in quite an anaerobic environment.

 

Regardless, IMO the way I deal with fungus is to open up the lens and clean it off!

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Nice, Mike. I never thought I'd be discussing free radicals and DNA damage here.

 

For mold, it's the short wavelengths as I mentioned. BUT, none of them simply kill mammalians cells directly at the low doses. The damage caused by superoxide radicals more likely initiates apoptosis.... I can't believe I'm actually bringing this up on this forum.

 

Later.

 

David

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