Coating problem, fungus? what is it?

[Ginette]

I'm not a specialist of lens defaults but what is this? A coating problem, fungus?
I didn't try to clean it, just want to know what is it before?
This is on the front of a Pentax 67 lens.
Thanks for the identification.

[Nathan Potter]

Looks like dendritic fungus growth to me. Has progressed from the edge of the glass front achromat between the cemented pair toward the lens interior. The haze along the edge of the dendrites may be an interference pattern.

Nate Potter, Austin TX.

[Ginette]

Thanks for the fast answer Nathan. I just received this lens so I will send it back. I just don't have any knowledge to handle this.
Look at first like a big fingerprint in the lens but looking closer with light, I saw the weird reticulation pattern.

[Leigh]

Yep, it's fungus, which makes long squiggly lines radiating (usually) from a common point.

Put it in a zip-lock freezer bag and put it well away from any other photo gear, like at the other end of the basement.
Fungus is contagious. Left in the open air, that lens will infect others.

- Leigh

[Ginette]

Yes thanks Leigh. I throw the original box with lining in the garbage, put the lens in a new box, ziplok it and put in a second box and wait the refund to send it back.

[Alan Gales]

Unfortunately, I've seen it before. It's fungus.

[ic-racer]

Just clean it off. It either leaves a permanent mark or not. You are not in control of what has already happened. If fungus, no need to be paranoid; the spores are everywhere, including your body. Just be sure to keep all gear in a location where spores don't germinate. For example avoid storage in a dark humid basement, etc.

[John Koehrer]

Unless you got a SUPER deal don't bother messing with it.
Return it and be done.

[civich]

I wonder if pentax 67 lenses have a particular susceptibility to fungus. I also have several of these lenses which developed severe fungal growth on the glass. None of my other lenses of different manufacture which lived in close proximity to the 67 lenses had any problem whatsoever. Perhaps a specific coating formulation which pentax used is to blame. -Chris

[hoffner]

Different glass types can have different readiness for fungus attack. Coatings don't have any different effect on it. Light is not necessary for fungus growth.
In your case the Pentax lenses probably had a different history and dirt coatings than the rest of your collection.
You can read to your heart's delight about "glass fungus" or "fungus on glass" googling those terms. And it's good stuff, even scientific studies.