Is this fungus?

Dear Forum

I just bought a Symmar-S 135/5.6 lens which either has poorly applied

cement or is a victim of a fungus. I've posted some pictures of the

edge of the rear element - http://www.photo.net/photos/mjob - and

would be very grateful if anyone with an expert eye could take a look

and let me know what they think.

Many thanks in advance,

Michael O'Brien<div></div>

It doesn't look like fungus. Fungus usually has a 'spidery' appearance, something clearly organic. What you have is just what you thought, and I doubt it will hurt performance.

Many thanks Pico. I've only found pictures of the spidery fungi you mention but other photonet discussions around this topic mention a "rare snow-like fungus" ...

 

MO

IMO this is "Schneideritis"<p>

make a search in Google<p>

http://www.google.at/search?client=firefox-a&rls=org.mozilla%3Ade%3Aofficial_s&hl=de&q=Schneideritis&meta=&btnG=Google-Suche<P>

regards<br>

Martin

It's got a mild dose of that as well of course Martin, but Schneideritis appears in the mount rather than on the glass itself.

 

MO

doesn't look like a fungus to me, looks more like condensation that has dried out and left a

residue. can you post a larger picture to give us a closer look?

I'm with George. That looks like dried crud and possibly some little chips too.

 

Schneideritis is bubbles in/separation of the black paint on the elements' edges, doesn't affect the elements' surfaces. Your "stuff," Michael, is on the surface.

Thanks guys, I agree my 'stuff' is (at least) on the surface. It's difficult to get a good snap of it but my very first impression was that the lentil was chipped around its edge because the larger dots appear crystalline, so I thought they were part of the glass. I've posted a closer detail entitled "fungus? 7c" at: http://www.photo.net/photos/mjob

If it's cement, then maybe a not-so-good repairer placed dots of cement around the edge of the lentil and a thinner film of cement crept out from these when pressure was applied to re-seat the lentil - the bit which looks like snow in the photos. If it's fungus then this creep is the beast heading towards the centre of the lens from its main concentrations at the edge. If it were condensation I'd find these concentrations - the dots - surprising.

In other words a picture's worth a thousand words - but not the snaps I've managed!

MO

looking at the larger picture the blobs are pretty much definitely cement from a bodged

repair. the other bits look very much like the gunk left behind when condensation

evaporated - i seen no fungus in that picture (i studied ecology so have a bit of expertise).

 

How you fix it, i don't know.

As the others say, it looks like either blobs of cement, small debris, or small chips. You could test for the last by feeling with a probe to see with these things are above or below the surface. It doesn't look like photos that I have seen of fungus on lenses.

 

Since these things are so close to the edge, I don't think that there is much need to fix them. Set the lens at the widest aperture that you will use for taking a photo, say f16, then position the lens at the largest rise or shift that you will use. Look through the back of the camera through the film gate at the aperture and move your head around to all edges and corners of the film gate -- does the aperture ever reach the very edge of the glass? If not, then when you are taking a photo, light rays used for the photo never pass through these debris. I think that is likely the case, so why worry about it.

The "wavy" stuff is undoubtedly separation in the cement/balsam. I have a couple of similar examples. The half-round artifacts are probably separation also, I have one lens that exhibts those in about the same place.

 

Steve

Thank you very much indeed for that Steve. I had the idea that this was something unusual: having surfed in search without finding anything similar. You have lost me a bit on the use of "balsam" though. If it means, in this context, the same as what I meant for 'cement' does that mean that essentially the optic is about to lose a lentil from its 'glue' coming apart?

 

You write that you have examples of this phenomena - are these lenses now beautiful paperweights or can you ignore the 'problem'?

 

Best,

 

MO

Michael, why do you use the word lentil? Its not the english word for the concept you apply it to. Lens or lens element.

 

In english lentils are a kind of seed, a major ingredient of a really nasty porridge (my opinion) and of slightly less nasty soups (also my opinion). Tastes differ.

<b>Dan Fromm</b> [...] <i> lentils are [...] major ingredient of a really nasty porridge (my opinion) and of slightly less nasty soups (also my opinion).</i><p>

 

<b>No soup for you!</b>

I agree it looks like separation. If it doesn't spread further it won't have any noticable effect on your photos. OTOH, if the seller didn't tell you about it then a refund might not be a bad thing to request.

By 'lentil' I mean lens element of course. Don't know where I picked up the habit of using that term, way back to college days I think. Anyway, 'lens element' from now on.

 

As for 'if' the fault will spread or not, I've no way of evaluating the risk... .

 

Best

 

MO

Lentil vs. lens - did you ever learn German, Michael? Because its the same word in German, "Linse".

Ja, though I may have picked it up from reading, in English, part of a book produced by Leica talking about lens design. Anyway, as lentil is a diminuitive of lens it makes sense to use it to describe part of a lens which is made up of lentils. Still, usage is meaning so I'll stick to lens element from now on.

 

BTW, anyone had experience of my 'cement' problem and can advise on likely outcomes?

 

TIA,

 

MO

Michael,

 

Glass elements used to be "cemented" with Canada balsam.

 

Steve

Thanks Steve. Is the effect on-going in the lenses you have effected by this?

 

Best,

 

MO

Michael,

 

No, as far as I can tell. Maybe it will grow, maybe not - but it certainly won't get any better! The glass can be recemented by Focal Point, Ultra Flat, and a few others but it's fairly expensive, not something you'd consider with a low to moderately priced lens.

 

Steve

Many thanks to all who posted in response to this query. In the end I concluded it was seperation in the cement that would probably never effect performance. But it might, so I returned it to the seller as the lens was only ever intended as a stop gap until I found a Fuji or Rodenstock 135mm with their greater coverage.

 

Again, many thanks for the helpful contributions.

 

MO