Learned the hard way that lens fungus spreads while you wait, not just on the shelf
I picked up a cheap 50mm at a flea market in Tampa and figured the haze inside was just dust, so I shot with it for about two weeks before popping the front element off. Turns out it was fungus and it had already started etching the coating, plus I may have cross-contaminated my other glass by storing them in the same bag. Has anyone here had luck stopping the spread with UV light, or is separation and a proper clean the only real fix once you spot it?
Man, a buddy of mine went through this exact thing with a used 85mm he bought online. He tried the UV lamp trick for a few weeks and the spots just kept creeping, so he ended up tossing the lens and pulling the rest of his gear out of that bag to air everything out. Once fungus gets a foothold the only thing that really works is getting it apart and cleaned, and even then you have to watch the ones that shared space with it for a while.