Is this Fungus?

Having never seen it before I would like to know if it is. I bought the lens on Ebay but when it arrived this morning there was this on the back element which will not clean off. I presume it is but just want to make sure before I contact the seller.
Thanks.

I don't know what it is, but the seller should have mentioned and showed it with a very clear picture in the add. I hope you can sort it out.
Martin.

That looks very much like fungus. It won't appear on the shot but will have a slight affect on contrast. If it was at the edge of the frame it would be less of a problem. I'd do some tests shots and see if you feel it's affecting quality if you're not happy ask for a refund or considerable discount.

If it is fungus, and it does look like it, don't get it anywhere near your other lenses. It is contagious.

If the fungus is inside the rear element it's probably part of an element group and can't be cleaned cost effectively as the groups are often glued together.

It looks like fungus to me. Is that the DA 16-45 you just purchased. :

No, its a Pentax-M 50mm f4 Macro.
It only cost $40 buy it now from usa with shipping but I just annoyed me nothing was said on the auction details

Just how contagious is fungus? I guess it spreads through spores but I have no idea when or why a fungus like this creates spores - isn't there something that will kill but not remove the fungus?

Mike

I'm with you Mike, i'm not sure how its spread but i do believe its contagious as i have seen bags where one lens was infected and after checking the others it was found in those also.
But these were bags left idle for a considerable length of time.

What is the consensus regarding the DA* lenses in regards to them getting fungus : They are well sealed i'm lead to believe and would expect it to be near impossible to get any spores inside them.

Am i talking crap or is this a known fact :

THe spores are everywhere in the air and might well be already inside the lenses when new.

We keep our current kit in Billingham bags, but little used stuff is on a open shelf, dry, with plenty of air circulation.

So what you are saying is they are just waiting for the right conditions to propogate :

Excellent article on fungus here.

John's quite right, the chances are all your lenses already have spores inside them (and have done since they left the factory), the trick is to stop the spores germinating and you can do this by not storing your lenses in damp, dark, warm conditions. There's no need to keep infected lenses quarantined - just make sure you don't repeat the mistakes with uninfected glass.

Older lenses are more prone to infection than newer ones due to the cements used inside the lens. Modern synthetic cements don't contain as many nutrients needed by the fungus to grow, hence you're less likely to see it develop on a DA lens than you are on a K or M (for example).

I've found that even infected lenses, once stored properly, will stop increasing in size; so if the infection isn't making a discernable difference to your pictures there's no reason why you shouldn't continue using the lens as normal. If it is affecting IQ then there are methods for removal outlined in the link I posted above - try the simplest first and work your way through.

Not mentioning the fungus in the eBay listing was a bit naughty I admit, but don't look at it as a death sentence for your new lens.

One trick I read of to kill the fungus is to leave it exposed to the sun (UV) for a while. It'll get hot, which might cause the greases inside to liquify so be careful. Leave the aperture wide open so that the black iris blades don't get heated directly by the sun.

The fungus is not removed but this procedure is supposed to kill it, then it appears to shrink, causing less of a problem to images.

Also, there are different types of fungus and it's not necessarily the fungus itself that can destroy a lens, more the secretions of the fungus, some of which are acid and 'eat' the coatings and effectively etch the glass.

Arguably the most common cause of fungal infestation in older lenses is the practice of supplying them with leather cases, in which they are stored. Leather harbours fungus spores.

Lenses should be stored in cool dry, and airy locations when not in use for a while.

Ah well, seller refunded me completely this morning and told me to keep the lens, dump it or give it away.

Excellent service. There are some good sellers around. I'd say you can't get any fairer than that.

You'll lose nothing by trying to clean it. The fungus is most likely on the insisde but if it's on the outside, try pure acetone (nail varnish remover) or methanol (Eclipse lens/sensor cleaning fluid).

If it's inside, you might be able to remove the rear element with the right tool(s). You'll almost certainly need a lens spanner and some care.

Its on the inside and I have no lens spanner so I will leave it in the drawer ... all on its own ... in solitude ... alone ... seperated from the others ... banished ... never to see the light of day again ... and all because it is unclean ...

Actually I tell a lie because it is (as you suggested) outside in the sunshine as I type.