Fungus on lens

[tor]

Hi everybody! I've been reading informative threads on this forum for a while but not until now did I join. Just got myself a 500 CM with an 80 CF lens. I chose the CF over the CB since the latter has 6 elements, the former 7.
When I examine the lens against strong light and tilt it so I don't get blinded, I can detect something on one of the elements. It could just be very small particles of dust that stuck to the glass over the past 15 years. But it's quite evenly spread over the surface. It is quite hard to see but it is visible if one consentrates the eye. So my question is:

What does fungus in a lens look like? If anyone have an image of such a thing you're welcome to post it. I've been told that a lens is beyond repair if fungus got hold. Is this true?

There is some normal dust particles in there but that does not bother me that much. Dust gets in everywhere as time passes. And its not excessive amounts we're talking about.

 

[toona]

>Hi Tor > > Fungus usually shows up as thin strands; a bit like a spider web. If it is well advanced, then you should be able to see it easily, often radiating from points. However, if it is in fact fungus and only a few tiny spots, then I would certainly imagine it to be cleanable with no problems. You say even distribution? Odd. A bigger problem might be lens separation or breakdown of the glue...but this should be obvious too.

I live in a warm and humid place and fungus can be a big problem, but can generally be cleaned, contrary to what some say. I have an OM 90mm f2 lens that seems to get it really easily and it has been cleaned a few times over the years. That is if it isn't TOO advanced. If so, it can leave a little bloom on the coating that does not affect imaging detectably (probably only top coating affected). I asked my repairer about the 'eating into the glass' issue that I have heard about but never seen and he said 'very rare' and only if left for a long time.

A good repairer should be able to tell at a glance.

Nick

 

[tor]

Hi Nick and thanks for the answer!

I have been to a reputable service center in Edinburgh today and had with me pictures of the problem made with a macro lens on my Nikon.

The repairman said its not fungus. It is most likely particles that has been expelled from the shutterblades during operation.
There was a pattern (very hard to detect, you need a macro lens to see it) but personally I think it's the same kind of pattern you see powdersnow form on a frozen lake if its a bit windy.

The dust was like an even, fine layer on the glass. He could see that it was on the back of the first group. Hence why it had come from the shutter. He said it should not affect picture quality notably.

It was that layered quality of the dust that I had not seen before and which confused me. This is natural since the Nikkors does not have any shutters in them.