Solar exposure,prevention of fungi and lens caps

[Joao]

Hello
I would like to share a recent finding.
It is common belief that direct sunlight may help prevent the growth of fungi on lenses. Based on that assumption, I have occasionally exposed some lenses to direct sunlight. I had a few ones recently facing direct sunlight, diaphragm wide open - and I left the rear plastic caps on in two of them (a Jupiter 135 and a Granit zoom) .
I found these tracks in the inside surface of the rear caps; I believe they are related to the apparent movement of the sun – the strong light, amplified/focused by the lenses, melted the surface of the plastic .The different positions of the tracks was probably due to different positions of the lenses in different days.
Image here

I can imagine the potential damage caused to shutter curtains if this was done with lenses attached to the cameras. Or the damage caused to any combustible surface left behind the lenses.
And a question: is there any solid evidence that this method is really valuable to prevent the development of fungi ??
Speculation (not really important) : could this be considered in some way a physical (not chemical) form of photography ?
Regards
Joao

 

[Clark.EE]

Fungi needs food.
Old Petroleum grease from helicoids etc.
I suspect that different fungi like/grow at different temperatures.
But it may help with some.
More likely to melt the old grease & cause more problems!

I suppose it is Photography, you are not the first to produce Solar/particle trails,
I dont think you will win any awards for it.

 

[Joao]

Fungi needs food.
More likely to melt the old grease & cause more problems!

I suppose it is Photography, you are not the first to produce Solar/particle trails,
I dont think you will win any awards for it.

Good point, I was ignoring the heating of the old grease...

"Physical" photography - it was a curiosity /conceptual digression, no more than that

 

[Mr_Flibble]

Fungus dies in Ultra violet light. It's a fact.

 

[maddoc]

I tried to kill what I thought could have been fungus behind the front element of my Summitar by radiating with a UV-B light source in the lab. The result after one hour of radiation was the formation of an air bubble from separation of the front doublet.

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[Freakscene]

Fungus dies in Ultra violet light. It's a fact.

Indeed, but coated camera lenses are terrible transmitters of UV. This is why to take proper UV photos you need a lens with quartz elements. It is very unlikely that an adequate dose of UV would get to any fungal spores or hyphae inside your lens.

Fungi need food - but there will always be lubricants in lenses. But they also need water, and if you store your lenses dry you can minimise the risk of fungi without risking your cemented groups, lubricants, back caps etc.

Marty

 

[sevo]

I tried to kill what I thought could have been fungus behind the front element of my Summitar by radiating with a UV-B light source in the lab. The result after one hour of radiation was the formation of an air bubble from separation of the front doublet.

That is rather unlikely to be immediately caused by UV, as glass is opaque to UV-B, so that the UV itself won't reach the cement layer. But as the energy is absorbed by the exposed lens element, you could have found a novel and dangerous way to create thermal strain in a cemented group (which is well known to cause separation).

 

[kuuan]

to prevent fungi to grow most importantly keep your lenses dry
but too much heat, as you found, can be damaging

 

[maddoc]

That is rather unlikely to be immediately caused by UV, as glass is opaque to UV-B, so that the UV itself won't reach the cement layer. But as the energy is absorbed by the exposed lens element, you could have found a novel and dangerous way to create thermal strain in a cemented group (which is well known to cause separation).

You are right of course, only UV-A is partially transmitted. Could have been a thermal strain effect, slowly heating of the lens head in an oven did not solve the problem.

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[Joao]

... but coated camera lenses are terrible transmitters of UV. This is why to take proper UV photos you need a lens with quartz elements. It is very unlikely that an adequate dose of UV would get to any fungal spores or hyphae inside your lens....

Thanks for clarifying this point. One more reason to change the practice of exposing lenses to sunlight.
regards
Joao