Fungus inside an objective

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Planapo
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Fungus inside an objective

Post by Planapo »

Hi folks,

In the following I will use the term 'objective' in a broader sense, i. e. for microscope objectives as well as camera 'lenses' . (Otherwise I would have to speak of a lens consisting of lenses. I don´t understand why in English one speaks of an objective only with respect to a microscope but calls the objectives for cameras 'lenses' which then consequently have to be lenses assembled from lenses or groups of lenses? :? )

Anyway, I´ve elsewhere read that if an objective is stored under bad, presumably too moist conditions, fungi can grow on the lenses within the objective, but hadn´t myself seen such an objective with fungal growth inside .

Now, recently I got an enlarger objective which looks fine from the outside, nothing to see on the rear or front lens. But if one looks through it directly into a light source, or looks inside it under oblique incident light, there is a kind of meshwork visible, consisting of what looks like fine fibres on the inner lenses, reminding of a cobweb or a thin layer of absorbent cotton. These fibres could be hyphae of a fungus.

I wonder if that is the fungal growth that I´ve read about? I´ve attached two pictures of the inside of the above-mentioned enlager objective. Maybe some of you who have more experience with such flaws of older objectives can tell me if that´s what internal fungus could look like?

Another question is how it will affect image quality? If I look through the reversed objective, I can use it as a fine magnifying glass, and can´t perceive any flaws. But I am aware that my eye/brain might compensate for flaws that will deteriorate the quality of an image recorded by the camera.

I´m looking forward to any of your replies on this topic for which I herewith thank you in advance already.

Best regards,
Betty

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rjlittlefield
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Post by rjlittlefield »

Betty,

Interesting! Thanks for posting these excellent pictures. I do not have much experience with fungus, but that is certainly how I would interpret this.

Generally speaking, with fairly thin lens designs, imperfections such as dirt, scratches, and fungal hyphae (?) like we see here do not significantly affect important lens properties like resolution. Their effect is to scatter a bit of light into what would otherwise be dark areas, reducing the image contrast and adding a bit of "fog". This can be largely corrected with a simple level adjustment in Photoshop. It is a good sign that you can look through the lens as a magnifying glass.

With thicker lenses, imperfections can turn into visible artifacts on images. The classic example is fisheye lenses, which have such extreme depth of field that the frontmost surface is almost in focus! Any bit of dirt or waterspotting can be disaster in that case. The situation is similar with microscope eyepieces, some places in the condenser train, and so on. It all depends on how close to being in focus the defect is.

BTW, the term "objective" is also used in telescopes. In both cases it means "the lens or system of lenses ... that is nearest the object being viewed" (quoting one of Google's definitions). The term is unusual with lens systems in cameras and enlargers -- Google finds only 14 (!) instances of "enlarger objective" and some 15,300 instances of "camera objective" (versus 4,960,000 for "camera lens").

The term "lens" covers both single- and multiple-element designs; in the latter case each of the chunks of glass would be called a "lens element" if it is important to distinguish.

--Rik

DaveW
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Post by DaveW »

See:-

http://www.chem.helsinki.fi/~toomas/photo/fungus/

http://www.mypentax.com/Fungus.html

One other problem in old lenses used to be delamination of bonded elements when the balsam cement used to partially fail, but is not so common with modern synthetics:-

http://www.microscopy-uk.org.uk/mag/ind ... ungus.html

DaveW

Leif
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Post by Leif »

The problem with fungus is that it can etch the glass, and of course it will get worse. It is possible to clean the lens if damage is light, and you know how to reassemble it again. That can be hard. But if damage is severe, then the contrast will be reduced possibly significantly.

It is best not to store it with other optics in case the fungus spreads.

I have a Nikon micro with something on an inner element, and I believe it is condensation of some sort, since heating has driven most of it away. Yours looks like fungal hyphae. Sadly.

I once bought a Nikon 3T diopter from an ebay seller. It turned out to be delaminating, the symptoms being coloured fringing around the outer areas. Fortunately the seller apologised and refunded all costs. I think he just assumed something he had not used for years was as he had left it.

Ken Ramos
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Post by Ken Ramos »

I would have to agree with DaveW, it does look like the lens cement is failing. I have seen similiar things in refracting telescopes and espcially older binocular objectives. I cannot be sure but it is a good guess that the cement is deteriorating. :( How it would affect and image? I think Rik has a very good handle on that. :D

Charles Krebs
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Post by Charles Krebs »

Looks like fungus to me. Enlarging lenses can be a little more prone to this because they frequently "live" in humid dark rooms, and get handled by hands that are not always 100% dry.

Planapo
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Post by Planapo »

Thanks guys for your helpful input!

Meanwhile I have sent the lens back and finally got my money refunded, after I had sent mail in a more resolute tone via my institutional email account. Seller had described the lens as "flawless", and then stated he hadn´t seen fungus inside and insinuated that maybe I could have changed the barrel part with the serial number to fake the photos and would send him back another bad lens for his own. :shock:

I experienced a similar incident a couple weeks ago... . Hmm, :-k seems quite a lot of people have terribly bad eyesight... well, at least when describing the stuff they wanna sell... :smt009

It were only lower costs with these items, but imagine handing over a decent sum for instance for a used MP-E 65, and then such a mess... #-o :-k

Cheers,
Betty

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