Originally posted by tibbitts I hope everyone who sends in a lens in for what appears to be decentering issues will report their experiences. Honestly I'm not sure decentering can be "fixed", at least without replacing a good chunk of the lens, because of how modern lenses seem to be composed of integrated element groups. I just don't know how much adjustability is built-in compared to older generation lenses. It would be interesting to hear from an expert on that issue.
My experience was that I couldn't get the lens fixed/replaced, even within warranty, because it wasn't deemed to be bad enough.
Regarding the 1 year warranty, remember that buying with a credit card (at least in the US) gets you a second year free. Of course that might just buy you a second year of not being able to convince the manufacturer to fix/replace the lens.
My experience would suggest you want to be dealing with a seller that will do an over the counter exchange if you judge the lens to be defective within 7 days of purchase. I use mail order, and Henry's gives me two weeks. Essentially, I don't want to pay for a defective lens. I am willing to pay for a lens that works perfectly. Not a lottery shot at a good lens, I don't care who messed up, bad at the factory, dropped during shipping , dropped in the sellers warehouse, I don't care where or how it got knocked out of alignment or it ever was in alignment, I am only willing to pay for a good lens. Henry's took back two Sigma 120-400's before I gave up and bought the 60-250. And I could have gone for a total refund of my money. The law in Canada says I have 7 days I believe, Henry's adds another week to that because it's mail order, what they think about the lens is irrelevant, if for any reason I say it's not good enough, even if I made a mistake and ordered a lens that wasn't good enough (as in the second 120 to 400, it was working up to spec, I just didn't like their spec), they take it back. That's what you want to be dealing with.
The day I get a new lens, I run it through the mill, closeups, distance shots, low light , into the sun and backlit subject... if there's any question in my mind it goes back.