I’ve been blogging about testing and taking apart camera equipment for almost a decade. Lensrentals.com has many thousand lenses these days, and they all get used frequently. When you have lots of lenses and they get used frequently, stuff gets inside them.
Usually the stuff that gets inside is dust. Our repair techs open up and clean dust out of more than 100 lenses a week. Not because the dust matters a bit in a photograph; it doesn’t. But because people still seem to think it does. People also, for reasons I can’t understand, seem to think that weather sealed lenses are less likely to get dust in them than non-weather sealed lenses. I’m not sure why they think this, but they do.
Sometimes the stuff that gets inside them is interesting and we get to blog about it. We found a spider, complete with web, inside a lens once and yesterday we got to add a new item to our ‘found inside lenses’ collection; a nice, fat, fly. And not just a fly inside a lens, but one way down deep inside a weather sealed lens. So deep that it took 4 hours of work to get it out.