I really don't know what to do. There is this used Tokina 28-80 f2.8 lens for sale but the front glass has some kind of smudge on it. It was personally cleaned by the owner plus cleaned by a camera shop and won't go away. But he says that it doesn't show up in any pictures. It would cost me about 1/2 the price of a new one. Thoughts please.
If you have a digital camera, ask to take a photo with the lens and then upload it to your computer and look at the smudged area at 100% crop to see if it is really invisible. Personally, I would never buy a used lens with an obvious defect on the glass (whatever I was told about it).
I always think on the black side. i.e. did the owner clean it with sandpaper to make sure the mark came off.
Glass is pretty tough, but you should see my 12 month old spectacle lenses under a 7 times magnifier.
Mmmmh