Fungus experts... need help

*Andi Lo* · 11-07-2009, 10:32 AM

Can some please let me know ehether this is fungus or separation? If it's fungus I am worried if it will affect my other lenses :/ The first side looks like fungus to me but the second one looks like defective coatins.. You can click on the picture for the fullsize.

Thanks!

wlachan · 11-07-2009, 10:40 AM

I am not sure, but you might look up the optical diagram of that lens and see if those are glued elements. If not, then it's fungus.

*Blue* · 11-07-2009, 11:28 AM

Andi,

I tend to agree with you but based on what I can see I'd say its inconclusive.

MattGunn · 11-07-2009, 11:32 AM

It doesn't look like fungus or separation but from these images it is hard to tell. It looks more like a coating related problem. Are these marks on the surface or inside the lens? There are quite a few ghost images of the spot so its hard to tell where they are from the photos.

*kristoffon* · 11-07-2009, 11:50 AM

the photos don't show much but if you care to take a look I posted a while ago about a lens I have thinking it had fungus but turned out to be just condensation

Did my 77ltd just become a paperweight?

*Andi Lo* · 11-07-2009, 01:46 PM

The markings are inside, I have cleaned the outside of the lens with lenspen. The first picture does have a reflection of itself in it. I worry about trying to do anything to it because I'd rather just return the lens... :/ Very sad as it's a very good copy Sigma 10-20mm.

@wlachan: I can't find the optical formula for it unfortunaely. Even if I did wouldn't it be hard to identify which of the glass has it?

I'll try to get a clearear picture again tomorrow.

forensicscientist · 11-07-2009, 01:58 PM

Any chance you know someone who has access to a microscope? Maybe at a University?? You ought to be able to confirm one way or the other under a basic stereoscope....

Maybe even just drop into the Biology Dept one afternoon and ask for some help.....?

Regards,
Mark

Ben_Edict · 11-07-2009, 01:59 PM

I cannot detect anything that should give reason to worry. No clear sign for separation and no funghus. What might be seen, but I am really not sure, where this ould be located inside the lens, are tiny bubbles, which you sometimes get, when the glue had not enough time to settle, before cured. I have seen exactly one other Sigma lens, which suffered (much more severely than your) from this. But if it is on the side of the lens, outside the light path, this would be only a cosmetic problem. But, hard to decide from the images.
Ben

*Andi Lo* · 11-07-2009, 02:06 PM

Originally Posted by forensicscientist

Any chance you know someone who has access to a microscope? Maybe at a University?? You ought to be able to confirm one way or the other under a basic stereoscope....

Maybe even just drop into the Biology Dept one afternoon and ask for some help.....?

Regards,
Mark

Brilliant... I'll do this first thing monday

@Ben: Thanks Ben, I'll try to negotiate a settlement with the seller as I really like the lens, and at the time I do need it (my employer wants me to shoot some architecture), but I still shouldn't pay full price for late pizza!

I'm actually not worried about image quality at all (I've tested the lens at all distances and foal lengths and it's excellent), but just the resale value of the lens, especially if it's fungus or element separation as those seem to reduce the value quite a bit. I'm worried about fungus infecting my other lenses too of course.

*Andi Lo* · 11-08-2009, 03:06 PM

Just found a site that has a defect similar to mine, but I'm not at all convinced that this one is fungus...
Fungus

The smaller one, the one that worries me more, I haven't found anything similar though. It looks like fungus but doesnt have the crystalline structure. It's more like a condensed haze, very confusing. It's also small that it's hard to photograph...

Here's my slightly better shot at it (right side). Again you can click on the picture after it opened for fullsize.

Got the optical formula from the sigma website
http://www.sigmaphoto.com/lenses/len...01&navigator=6

Looks like those parts aren't glued... so it's not element separation.

Thanks to everyone who helped so far

conclusion: : Dave, the pentax repairman from halifax told me that it's just fingerprints left by whoever serviced it last. How clumsy of them! so good ending after all

Got a hygrometer for my lenses to make sure that I'm not letting any fungus growth.. just in case.