Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!
SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Can a UV lamp kill fungus and make the lens safe for use?
Post new topic   Reply to topic
Home   Manual Focus Lenses
View previous topic :: View next topic  


PostPosted: Thu Nov 13, 2014 6:26 pm    Post subject: Can a UV lamp kill fungus and make the lens safe for use? Reply with quote
Hi,

I found some fungus it my recently acquired Canon FDn 85/1.8, it's located somewhere in/on the inside of the front lens group and it's limited to the edge. I doubt that it will have much if any impact on the image but I hesitate to use the lens.



I'm going to have to find the time to remove the front group and clean it but for now I lack the time and the tools.
I'm looking for a way to make the lens safe for use (without risking the fungus' spread to other gear) without taking it apart.
I've kept the lens under a 25W UV-lamp (CCFL) for the last week and the fungus appears to have become somewhat less dense.



Now I'm wondering whether the UV light (it's a cheap lamp without documentation so I don't know it's emission spectrum) is killing the fungus and perhaps even eating away at it's remnants.

If it kills off the fungus colony, the lens would at least become safe for use, so that's the question:

CAN IT?


regards
Jan


PostPosted: Thu Nov 13, 2014 6:54 pm    Post subject: Reply with quote
Interesting question, I have often wondered in the past , how infected lenses would contaminate a camera and how quickly this would evolve into a problem. How virulent is fungus?, does it require an existing contamination, ie, dust etc to proliforate?.

I personaly think that if it is easy to remove, do so. If it puts the lens at risk, leave it to a more competent technician or just live with it, if the cameras value is not of great significance.


PostPosted: Thu Nov 13, 2014 7:11 pm    Post subject: Reply with quote
bychance wrote:
Interesting question, I have often wondered in the past , how infected lenses would contaminate a camera and how quickly this would evolve into a problem. How virulent is fungus?, does it require an existing contamination, ie, dust etc to proliforate?.

I personaly think that if it is easy to remove, do so. If it puts the lens at risk, leave it to a more competent technician or just live with it, if the cameras value is not of great significance.



The front group is supposed to be easily removable on the FDn 85/1.8 but I need to get the right tools and find some quiet time to do it. There's a lot of dust in the lens already...

Until I find the time to open it up, I can leave the lens under the UV lamp. It would be good to know after how much time I could consider the lens safe and start using it.

The rear element moves with the focus so there will be some air movement between the back of the lens and the inside but the fungus is quite far from the back of the lens and it hasn't spread across lens surfaces until now. Does anyone know the internal construction of this lens?


PostPosted: Thu Nov 13, 2014 7:48 pm    Post subject: Reply with quote
Folks, fungus spores are always present in the air. They simply don't develop in reasonably dry environment, develop in the humid environment. The worry about contaminating other lenses with fungus through air contract is just a prejudice born out of nothing. Fungus is not a lens flu.


PostPosted: Thu Nov 13, 2014 7:55 pm    Post subject: Reply with quote
Yeah I have some pretty fungus-y lens in my collection, and my non-fungus-y lenses have never "caught" it. If everything is stored properly it's not going to grow or spread. I think most fungus is probably dead by the time we find it, though I can't prove it.


PostPosted: Thu Nov 13, 2014 8:36 pm    Post subject: Reply with quote
fermy wrote:
Folks, fungus spores are always present in the air. They simply don't develop in reasonably dry environment, develop in the humid environment. The worry about contaminating other lenses with fungus through air contract is just a prejudice born out of nothing. Fungus is not a lens flu.


Of course they are but there's a difference between having a small number of them floating about and having a dense colony of them <10cm from my sensor...

If I can kill the colony, I can start treating the 85/1.8 like my other lenses without incurring any additional risk (beyond the ever-present background-risk of fungus growth).


PostPosted: Thu Nov 13, 2014 9:46 pm    Post subject: Reply with quote
Even if every bit of fungus that is touched by the light has been killed, there may still be a living colony in the shadows, plus the acid that is made from the fungus may still be present and eating away at the coating/glass till it's clean.


PostPosted: Thu Nov 13, 2014 11:44 pm    Post subject: Reply with quote
Lightshow wrote:
Even if every bit of fungus that is touched by the light has been killed, there may still be a living colony in the shadows, plus the acid that is made from the fungus may still be present and eating away at the coating/glass till it's clean.

Well, until I get around to cleaning the insides, it's better than nothing.

Wikipedia says this:
Quote:
240–280 nm: Disinfection, decontamination of surfaces and water (DNA absorption has a peak at 260 nm)
so I probably need a UV source with some emissions at 260nm.
Quote:
The common fluorescent lamp relies on fluorescence. Inside the glass tube is a partial vacuum and a small amount of mercury. An electric discharge in the tube causes the mercury atoms to emit ultraviolet light. The tube is lined with a coating of a fluorescent material, called the phosphor, which absorbs the ultraviolet and re-emits visible light. Fluorescent lighting is more energy-efficient than incandescent lighting elements. However, the uneven spectrum of traditional fluorescent lamps may cause certain colors to appear different than when illuminated by incandescent light or daylight. The mercury vapor emission spectrum is dominated by a short-wave UV line at 254 nm (which provides most of the energy to the phosphors)
So a CCFL starts out with the rigth wave length (~254nm) but it mostly converted to the wrong wavelength
Quote:
Blacklights are a subset of fluorescent lamps that are used to provide near ultraviolet light (at about 360 nm wavelength). They are built in the same fashion as conventional fluorescent lamps but the glass tube is coated with a phosphor that converts the short-wave UV within the tube to long-wave UV rather than to visible light. They are used to provoke fluorescence (to provide dramatic effects using blacklight paint and to detect materials such as urine and certain dyes that would be invisible in visible light) as well as to attract insects to bug zappers.
The usual cheap UV-bulbs appear to be blacklights (sold as party supplies), so those emit the wrong kind of UV.
Quote:
350–370 nm: Bug zappers (flies are most attracted to light at 365 nm)
UV-lamps meant for bug zappers are out too...
Quote:
Germicidal UV is delivered by a mercury-vapor lamp that emits UV at the germicidal wavelength. Mercury vapour emits at 254 nm.
Quote:
These low-pressure lamps have a typical efficiency of approximately thirty to forty percent, meaning that for every 100 watts of electricity consumed by the lamp, they will produce approximately 30–40 watts of total UV output.
THERE WE GO!

So the best chance to kill fungus - if UV can kill fungus through the lens glass at all - is a lamp like this one (or a stronger version. Since CCFLs only get longer, high-pressure mercury-vapor lamps would be the best option but those are rather expensive...)

Quote:
Characteristics
• Issued short-wave UV radiation with a peak of 253.7 nm (UV-C) for sterilization
• glass bulb of the lamp filters out the 185 nm ozone-forming region
• Internal protective coating reduces the deterioration of the UVC-yield
• lamp is provided with warning UV-C radiation

Application
• destruction or deactivation of bacteria, viruses and other micro-organisms
• Air and surface disinfection in hospitals, bacteriological research and in the pharmaceutical and food-processing industries such as dairies, breweries and bakeries
• disinfection of drinking water, wastewater, swimming pools, air conditioners, refrigerators, packaging materials etc.
• For use in many photochemical processes


I think, I'll get these two and try it:
http://www.amazon.de/gp/product/B001VTPDX8/ref=ox_sc_act_title_3?ie=UTF8&psc=1&smid=A3JV61L0NEVASN
http://www.eoffice24.com/tischleuchte-brilliant-job-klemme-titan.html


PostPosted: Thu Nov 13, 2014 11:58 pm    Post subject: Reply with quote
Mos6502 wrote:
Yeah I have some pretty fungus-y lens in my collection, and my non-fungus-y lenses have never "caught" it. If everything is stored properly it's not going to grow or spread. I think most fungus is probably dead by the time we find it, though I can't prove it.


Nothing living on the planet can survive without water, but no one seems to know how long fungus can stay dormant before it dies i.e. how long does it takes to die if kept in a dry place.
We need someone who can use an electron microscope at work Wink


PostPosted: Fri Nov 14, 2014 12:06 am    Post subject: Reply with quote
Excalibur wrote:
Mos6502 wrote:
Yeah I have some pretty fungus-y lens in my collection, and my non-fungus-y lenses have never "caught" it. If everything is stored properly it's not going to grow or spread. I think most fungus is probably dead by the time we find it, though I can't prove it.


Nothing living on the planet can survive without water, but no one seems to know how long fungus can stay dormant before it dies i.e. how long does it takes to die if kept in a dry place.
We need someone who can use an electron microscope at work Wink


Meh, just get me a gamma ray source, something like this should do!


PostPosted: Fri Nov 14, 2014 1:08 am    Post subject: Reply with quote
I read somewhere recently that someone had got rid of fungus by shining a laser pointer at it. They claimed it removed the fungus.
But......this could be "I read it on the internet so it must be true" bullshit, and we all know that lasers can be dangerous.


PostPosted: Fri Nov 14, 2014 1:13 am    Post subject: Reply with quote
Lloydy wrote:
I read somewhere recently that someone had got rid of fungus by shining a laser pointer at it. They claimed it removed the fungus.
But......this could be "I read it on the internet so it must be true" bullshit, and we all know that lasers can be dangerous.

Yeah, I''m not going to point a laser stronger than class 1 (actual class 1, the cheap ones that are sold as class 1 vary widely in actual power...) at a tube full of reflective surfaces of varying shape...


PostPosted: Fri Nov 14, 2014 7:18 am    Post subject: Reply with quote
Boris_Akunin wrote:
...Yeah, I''m not going to point a laser stronger than class 1 (actual class 1, the cheap ones that are sold as class 1 vary widely in actual power...) at a tube full of reflective surfaces of varying shape...


Wise decision Smile

Please also use the UV-C lamp with care. I am the laser-safety and safety manager at work. I worked with a deuterium lamp, and read all that safety stuff. Don´t take it easy with UV radiation safetym and take care for the ozone dangers too.
Aspergillus Niger (at least one kind of [urlhttp://www.4photos.de/camera-diy/Lens-Fungus.html]glass fungus[/url]) needs a very high dose of UV radiation.


PostPosted: Fri Nov 14, 2014 1:02 pm    Post subject: Reply with quote
Industrial UV lamps (for water treatment and similar) are very powerful and more harmful to you than you might realize. I´ve worked with relatively weak UV lights and the permissible exposure to bare skin is measured in seconds per day. Be carfeul.

Also, consider that most glass absorbs UV light, so it may actually never reach the fungus inside the lens.

To keep your camera sensor free from fungus derived from the lens, simply clean the rear element (if it is even infected, most fungus I´ve seen has been inside the lens).

The probabality of a fungus spore finding its way out from inside the lens is probably much lower than that of an air-borne, naturally occuring, spore floating around in your room and landing inside your camera. Neither of which is likely to cause any fungal growth on your sensor.

If you do take your lens apart for cleaning the fungus, start with something "mild" like alcohol. I´ve cleaned many lenses from fungus using 70% ethanol (sometimes letting the infected lens "soak" for a while by placing a damp piece of soft paper on top of the lens surface). No need for ammonia, hydrogen peroxide and other nasty chemicals before you´ve tried alcohol.

One of the myths associated with lens fungus is that it has to be killed in order to be removed (the reason for using harsh chemicals), which is simply not true. Just wipe it off like any other stain, although it may require some soaking to dissolve properly.


PostPosted: Fri Nov 14, 2014 2:32 pm    Post subject: Reply with quote
ZoneV wrote:
Please also use the UV-C lamp with care. I am the laser-safety and safety manager at work. I worked with a deuterium lamp, and read all that safety stuff. Don´t take it easy with UV radiation safetym and take care for the ozone dangers too.

So the lamp that I'm using now is fairly safe (I don't exactly stare at it...) but the more useful lamps (germicidal ~254nm lamps) are also the most dangerous.
I'll set up the "treatment space" in a closed cupboard and set up the lamp so that I can switch it on and off before I open the cupboard. That should keep my eyes protected.
Quote:
But Aspergillus Niger needs for example a high dose UV radiation, 132 mWs/cm²


So, assuming it's the worst kind of fungus, how long does the treatment have to last?
All I still need to estimate that is a rough figure for the UV-absorption of the lens glass, any ideas?

I've got a 11W germicidal UV-C lamp (peak at 254nm) -->
Quote:
Short wave ultraviolet lamps
A shortwave UV lamp can be made using a fluorescent lamp tube with no phosphor coating. These lamps emit ultraviolet light with two peaks in the UVC band at 253.7 nm and 185 nm due to the mercury within the lamp. Eighty-five to 90% of the UV produced by these lamps is at 253.7 nm, whereas only five to ten percent is at 185 nm. The fused quartz glass tube passes the 253 nm radiation but blocks the 185 nm wavelength. Such tubes have two or three times the UVC power of a regular fluorescent lamp tube. These low-pressure lamps have a typical efficiency of approximately thirty to forty percent, meaning that for every 100 watts of electricity consumed by the lamp, they will produce approximately 30–40 watts of total UV output. These "germicidal" lamps are used extensively for disinfection of surfaces in laboratories and food processing industries, and for disinfecting water supplies.


--> I'll get 11*[0.85...0.9]*[0.3...0.4] = 2.8...4.0W of UV around the 254nm peak.

If I lay it straight across the front element, I can cover ~1400mm² of the front element's surface area, the lamps total surface area is ~20000mm² so in the worst case (no additional exposure through reflection behind/around the lamp) the lens will be exposed to 0.2W to 0.3W of UV around 254nm.

Assuming the fungus-infected surface is as large as the front element (~1500mm²), the lens should receive at least 13 to 20 mW/cm².
If that were to hit the fungus directly, the 132mWs/cm² exposure would be reached in 7 to 10 seconds... I've got weeks!

Let's say I let the fungus roast for a week, the lens would receive 7862400 to 12096000 mWs/cm² or about 60000 to 90000 times the required dose without glass in between. The lens glass could absorb or scatter 99.9983% to 99,9988% of the UV and the fungus would still get it's lethal dose.

So, what's a realistic (worst case) absorption/scattering rate for the 4 or less thick lens elements between lamp and fungus?


PostPosted: Fri Nov 14, 2014 4:36 pm    Post subject: Reply with quote
Your calculation does sound good.
But transmission for 254nm is very low for most optical glass.
Take for example BK7 glass, for example for 10mm thickness - no data for 250..260nm:
310nm: 57.4%
300nm: 29.2%
290nm: 6.3%
No further measurments given - even with wavelength values down to 250nm in the datasheet. Other glass even has last data at 350nm. It seems they give values as long as their transmission is 0.1% or higher.

Aside from the glass itself the antireflection coating is also not optimized for 254nm UV transmission. So there will be another low percentage factor.

For lenses with fungus I try to clean the fungus, and afterwards give it some sun UV bathing - fungused surface directly facing the sun. Likely with no big effect - but also with no cost or high effort.
But as main factor I also see correct humidity for storage.


PostPosted: Mon Nov 17, 2014 4:02 pm    Post subject: Reply with quote
Right, my UV treatment space is set up, I think this should be safe enough for my eyes (for obvious reasons, the pictures show a normal lamp instead of the UV-C lamp):









I'll put some aluminium foil under the lenses to reflect some UV back up the lens, all other surfaces are either wood or cardboard.
AFAIK, wood and paper/cardboard should mostly absorb UV rather then reflect it.

The lens next to the 85/1.8 is a Minolta MC 28mm f/2.5 with a slight yellow tint (due to radioactive glas elements), UV-treatment is supposed to help with that...

EDIT:
Here's the setup in action:



Obviously, I took the photo without looking.

Note:
My setup should deliver at least 130W/m² of UV-C to the lenses' front elements.
At sea level, daylight (at the equator, around noon) contains ~80W/m² of UV-A, ~4W/m² and <1W/m² of UV-C.


PostPosted: Mon Nov 17, 2014 7:14 pm    Post subject: Reply with quote
Nice looking setup. Does the lamp get hot when used? If so, have you thought of ventilation inside the cabinet to avoid melting the grease inside the lens(es)?


PostPosted: Mon Nov 17, 2014 8:18 pm    Post subject: Reply with quote
sceptic wrote:
Nice looking setup. Does the lamp get hot when used? If so, have you thought of ventilation inside the cabinet to avoid melting the grease inside the lens(es)?


The lenses feel slightly warm after a couple of hours, that's it, It's just an 11W CCFL after all.
I'll put a thermometer next to the lenses but I doubt it'll ever measure anything but room temperature...


PostPosted: Mon Nov 17, 2014 9:33 pm    Post subject: Reply with quote
sceptic wrote:


Also, consider that most glass absorbs UV light, so it may actually never reach the fungus inside the lens.



Bingo!! You nailed it. That's the controlling paradigm. Dunno whether UV will kill fungus or not. It might. But UV cannot kill fungus if it is unable to REACH the fungus!!

Except for fungus on the front of the front element, or on the rear of the rear element, of any lens, the first step to try a UV light kill is:

1. Disassemble the lens Wink


PostPosted: Mon Nov 17, 2014 10:02 pm    Post subject: Reply with quote
guardian wrote:
sceptic wrote:


Also, consider that most glass absorbs UV light, so it may actually never reach the fungus inside the lens.



Bingo!! You nailed it. That's the controlling paradigm. Dunno whether UV will kill fungus or not. It might. But UV cannot kill fungus if it is unable to REACH the fungus!!


Well, UV-treatment seems to clear yellowing induced by radioactive lens elements... UV-absorption can't be 100%.
In typical glass, absorption rates are lower for UV-A and that's what normal UV lamps emit (used as blacklights and in bug zappers, peak around 365nm). I'd guess that most most people who have tried UV light on their lenses have used normal blacklights.
If UV-A is what kills the fungus, I would need a stronger UV-A (~365nm) lamp.

On the other hand, most UV sources (including the sun, after it's past the atmosphere anyway) emit very little UV-C. UV-C is also the most lethal kind of UV for micro-organisms. If UV-C is what kills the fungus, my setup should be far more effective than a normal UV source or sunlight.


EDIT:
I've changed the setup a bit



PostPosted: Wed Nov 19, 2014 1:18 am    Post subject: Reply with quote
It's been running for two days and there are no temperature problems, the thermometer that I've placed right next to the lenses hasn't moved beyond the 20°C mark (the room temp. is ~16-19°C) and the lenses still only barely feel warm to the touch (below 30°C, I think).





There is no smell of ozone, the lamp's 185nm filter seems to be working. So if this turns out to work, ozone procuction inside the lens is probably out as a cause. (And if it doesn't work at all, UV-C is out out too and high intensity UV-A remains as the only non-invasive option to try)

BTW, it's interesting to see the difference between the blueish light reflected off the aluminium foil (alu is highly reflective across the UV spectrum) and the greenish light reflected of the wood and cardboard (high absorption in the UV spectrum, apparently also at the visible edge).


PostPosted: Thu Nov 20, 2014 9:37 pm    Post subject: Reply with quote
This is interesting - it's an article on lens fungus from a guy that does a lot with microscopes and photography - the web site is a mine of useful information if you're into micro photography.

The article on fungus shows a horribly fungused lens from a machine that projected halogen light, high in UV.

http://www.truetex.com/lens_fungus.htm

And the rest of the site is here

http://www.truetex.com/micad.htm


.


PostPosted: Fri Nov 21, 2014 12:15 pm    Post subject: Reply with quote
First status update:
There's no visible change in the fungus, idk if it's dead or alive but it's definitely not disintegrating.

My two yellowed lenses (Minolta MC 28/3.5, Soligor 17/4) have improved a lot, the tint is almost gone in both.
I've had the Soligor under a UV-A lamp (25W, peak output around 365nm) before without any change. UV-C seems to work a lot better.


PostPosted: Fri Nov 21, 2014 1:57 pm    Post subject: Reply with quote
Perhaps it kills fungus but does not disintegrate the remains?

I remember when I worked as maintenance guy for the clean water supply division for a while ( I usually worked sewage treatment ) we had a lot of boreholes where the disinfection was done with UV lamps, the water was passed over the lamp and became fit to drink. But it did not remove any discolouration in the water or remove particles by breaking them down. We had to filter to remove that.
Some boreholes in very agricultural areas did have high levels of organic impurities, and UV was favoured over chlorination - it killed everything.
Post new topic   Reply to topic
Home   Manual Focus Lenses
Goto page 1, 2  Next
Page 1 of 2