I dunno, maybe I'm too hippy looking, or because I live way out in surburbia and never went to art school with the punks behind the counter, but it seems clerks at the big pro shop in the city brush me off like a wino. Whereas I've had some back and forth discussion, one guy even suggested that what he was selling probably wasn't what I wanted and sent me an url to a different lens than his.
In the old days I heard about guys who would buy a hasselblad lens and test it, return it for another till they found the one they liked. try that now.
some lenses do have a rep for diviation from the specs, I don't know that a local store will let you go through them to find a good one, so with ebay you could buy one and test, if it sucks, put it back up for auction.
In my medium format days I would buy lenses, every one of them from studio closing sales and ebay, remember early days of ebay, before digital photos? Before feedback? I sent $1,000 money order to guy with a po box and got back 2 wide angle mamiya lenses in great condition. I did however buy my bods new.
I would buy meters new.
Normally I try to be informed before going in to buy, and on those occasions when I do go in with specific this and that, the clerks want to tell me that something else is better. Now usually I pick my object of desire because the last workshop I went to half the class has one, and while it maybe possible that half got one for the simple reason the previous workshop instructor was sponsored by the maker of it, that's still a powerful network of reinforcement, its why wacom is the only graphic tablet worth mentioning these days, probably why apple still hangs on...but that's a topic for another post.
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