Lens Dilemma

[joho35mm]

I wondering if I could get your feedback on a particular lens issue that I have. I recently got a nice Canon EF 50mm 2.5 macro for a steal on Ebay - the seller was offering it for about $80 less than the usual market price, so I jumped at it. The arrived completely as described, except for a few "dust specks" in the rear element. On closer inspection, I found that the dust specks were really fungus spores, showing tiny rings of outgassing. Now, the lens is wonderfully sharp and works just fine. I have two options now:

1. Return it. It's still within the refund period, and the fungus might cause trouble in the future.
2. (The more interesting option). A friend of mine at UC Berkeley works in a lab with a UV spot machine. She's offered to take the lens and shoot it with high-intensity UV rays for 5-10 minutes to see if it'll kill the fungus before it grows beyond "dust speck" size. I figure this might be a viable option, since the spores are in the rear element.

What do you all think?

[LarryD]

Put it under a strong UV light and move on.....

[martolod]

what larry said.

[sandeha]

Yup, killing them is not majorly difficult.  Fungus (AFAIK) is only a big issue when they've already done damage to the coatings.

[Santiago Montenegro]

I killed my fungii in that very same lens with lots of sunlight.

If I was a SLR person, I'd use it all the time. What a wonderful lilttle lens it is!

[joho35mm]

Thanks for the input. I have the lens on a shelf right now in direct sunlight (won't be able to take it to the lab until Thursday). Just out of curiosity, how much sunlight did you exposure your lens to, Santiago?

And a few sample photos from the lens, taken yesterday: