Looking for some advice here. I have an old Sigma EF mount 70-200mm f/2.8 EX lens, which I bought way back in 2001. I haven't used it for years but the other day I took it out for some landscape shooting and when I got the images into Lightroom I could see that something was definitely off, so I took a close look at the lens and saw what looks like a patch of fungus on one of the rear elements. Bother, blast etc. I attach a photo of the offending lens. It looks much worse in the photo than it does in normal light - I took this on a light table and angled the camera just-so to catch the light.
I emailed a few UK camera repair outfits plus Sigma UK as well, to ask if cleaning / repair was possible. Sigma wrote back to say sorry, no, the lens is so old we won't have parts for it. Two others wrote back saying yes, send it in and we will clean it up for you no problem. One of those quoted £120, the other just said they would give me an estimate once they had the lens. Finally, another repairer wrote back saying that while they could clean it they didn't recommend it, because once a lens has fungus it always comes back very quickly and they didn't want to take my money for what would be in effect a useless repair.
I'm curious if anyone here has experience of having a fungus infested lens cleaned up - did it work and did the infestation come back anytime soon? If a repairer is telling me not to bother then on the face of it I should take that seriously, but maybe they are being over cautious.
What do folks here think?