Originally posted by mkaresh Thanks for the responses. Not sure about the coating damage--seems like the fungus is on the inside, and isn't coating only on the outside surface? Or the inside surface of the front element is also coated?
Is this likely to continue spreading? Or probably happened a while ago and dead now?
Good lenses have all lens surfaces coated. With modern lenses sometimes the outer lenses have an extra coating to help keep dirt off etc but the coating to improve the optics is on all surfaces.
Fungi produce spores, which can lie dormant for decades before springing back to life, so it's hard to say. The best thing to do would be to clean it, but if you don't know how to take the lens apart yourself then that can be risky or expensive.
Personally, I would send it back as I wouldn't want a fungus-infected lens in my cupboard spreading spores to all my good lenses.