This lens would be great if it was good, but it simply isn't, with not even a 5X7 worth keeping. Too bad, the zoom range is unique and very useful.
If you insist on spending your money on this lens, make sure you buy from a shop that will take it back, or at least exchange it. If you're lucky and get a good copy, you got yourself a good buy. But you can just as easily end up in my shoes, with a lens that in fairness, can not even be re-sold. Total investment lost, small as it was. Will take it apart one day I'm bored, to learn more about lens construction.