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fungus cure

Discussion in 'Lens Matters' started by mediaman, Jul 16, 2021.

  1. mediaman

    mediaman Well-Known Member

    I read a while ago about lenses having fungus in them, and it was mentioned that leaving it in bright sunlight, the UV would eventually eliminate that fungus...So, a question, would a "black light" produce a faster end result ?
  2. GeoffR

    GeoffR Well-Known Member

    With enough intensity, yes, but I doubt you will be able to get one that has a high enough intensity.
    Petrochemist likes this.
  3. PeteRob

    PeteRob Well-Known Member

    Might, not would. Beware of fire risk.
  4. John Farrell

    John Farrell Well-Known Member

    I ran a test, shining a UV torch in a fungused lens, and wrote about it here (the photographs are no longer visible)

    The light from the torch had no discernable effect on the lens fungus. I normally dismantle the lens and clean the elements, initially with a domestic glass cleaner, but with meths, fuelite and acetone available. Once, I had to remove the fungus residue from a couple of CZJ Biotar lenses with a light rub with toothpaste - the lenses worked fine afterwards.
    zx9r likes this.
  5. Petrochemist

    Petrochemist Well-Known Member

    UV torches & simple black lights are generally significantly lower in UV intensity than sunlight.
    We used to have an 'isomeration cabinet' at work that had multiple high intensity UV lamps (set up to only run with the lid closed for safety) that would probably be more effective than sunlight but sadly it got ditched over ten years ago.

    UV LEDs also have potential probels as they tend to give just a single narrow band of UV light. Get the wrong band & either it won't be energetic enough to have any effect or the glass will absorb nearly all the UV... It's a balancing act that broad spectrum sources like sunlight avoid.
  6. nimbus

    nimbus Well-Known Member

    Fungus also can make it's insidious way into coatings and even glass over time. I have a degree of paranoia where fungus in lenses is concerned, a bit of dust doesn't overly bother me though.
  7. Benchmark

    Benchmark Well-Known Member

    That sounds like a QUV tester or 'accelerated weatherometer' used to test paints and plastics for weathering and fading. The old machines with carbon arc lamps in them were the best.
  8. pixelpuffin

    pixelpuffin Well-Known Member

    Fungus terrifies me
    All my kit is stored inside huge plastic containers, each container has a dozen or more giant 50g sachets of silica gel. I make a point of NEVER leaving any kit inside camera bags when not in use. My fear is that bags can wick up humidity (moisture) alas it’s a risk I won’t even contemplate.
  9. Benchista

    Benchista Which Tyler

    UV doesn't make fungus disappear, but it deactivates it, so it won't spread and won't etch glass if it hasn't already.

    The threat of fungus in the UK is not really all that great. I've got literally hundreds of lenses, and never had fungus develop in any of them. The couple I've - knowingly - bought with fungus I've deactivated with sunshine, my favourite being an M42 25mm Flektogon.
    Now if I lived in say Kuala Lumpur, I might justifiably be paranoid about it, but not with UK levels of year-round temperature and humidity.
    zx9r, Petrochemist and peterba like this.
  10. peterba

    peterba Well-Known Member

    You've never lived in Devon then, Nick? ;) :D I've had two lenses fall victim to fungus over the years. One was flatly refused for p/x by a camera company, while the other was accepted, but with a major reduction in price for dealing with the fungus. All this, despite storing the lenses with (regularly renewed) silica gel. :( Admittedly, these were the only two lenses out of, probably, 25 or 30 lenses, but it was still a PITA. I should point out that the average Relative Humidity in these parts is around 100000000000000000000%. :D
  11. Petrochemist

    Petrochemist Well-Known Member

    Possibly very similar in nature, but the role for ours was to produce a specific chemical change in a customs marker to allow for analysis. Our unit was built in house.
  12. PeteRob

    PeteRob Well-Known Member

    No it's not. Possibly, if the air were very free of particles (most common condensation nuclei) , you could get RH slightly over 100% before condensation occurs but only by a few percent. More water in the air than that and it's a two-phase mixture (fog).
  13. pixelpuffin

    pixelpuffin Well-Known Member

    But, is it not true that most multi coated lenses will block the UV wave length thus rendering a UV light source safe to fungus?
  14. peterba

    peterba Well-Known Member

    I can't believe that you took that comment seriously, Pete! :confused: I purposely typed a stupidly large number of zeroes, in order to avoid any doubt.
  15. peterba

    peterba Well-Known Member

    ............... unless, of course, you were being as silly as I was! :D
  16. Petrochemist

    Petrochemist Well-Known Member

    Glass itself blocks most UV, with practically no UV of wavelengths below 300nm making it past just 2mm of glass. When we get to wavelengths below 190nm even just a few inches of air will absorb all the UV.
    Above 300nm UV will travel a fair way through lenses, even multi coated ones reducing in intensity steadily as it goes. Sunlight or intense artificial UV sources can have a useful effect over time.

    I don't know precisely which wavelengths are needs to affect fungus, it may well be that some visual light at the high energy (blue) end of the spectrum will also work. Most lenses transmit reasonably well by the time you get to 450nm which isn't that far from UV. I've tried measuring the transmission spectra of some of my lenses using kit at work only two of those tested were modern multicoated lenses but both of these gave some transmission down to below 350nm through the entire lens. The best UV transmission I got from any tested (a Nikkor enlarger lens specifically chosen for reported good UV transmission) gave 1% transmission at 305nm, & over 50% at 350nm.

    It does seem the coatings can reduce the UV transmission significantly but it certainly doesn't stop it entirely & the general opinion from countless trials is that fungus is typically killed off by a few days of daylight. As long as some minor care is taken to prevent the lens starting fires there's no harm in trying this approach - keeping the lenses dry should also prevent further growth.

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