Originally posted by Frater Such a Tamron sounds after my taste
Spocky, were you lucky with your first copy, or if not, how many other copies did you have to send back before you got such a sweet one?
I've used 3
I had to replace one was a bit off, the other 2 were fine though
Like all lenses QC can play a part, so it's not a shock that there is some variation.
But certainly on the good ones f2.8 is great even at 50mm just fine and sharp mostly across to the edges just a very tiny fall off extreme corners, f4 clears that up but for most purposes few would notice unless you take brick wall shots, even then I've never had an issue in real world use. At the wide end of course you would tend to stop down for landscape shots (but watch out for that focal plane distortion) Decentering can be an issue on any lens, but it's quite easy to spot that problem when one side is notably softer than the other, few lenses are absolutely perfect, but you should know if there is something wrong fairly quickly.
In some cases AF issues can be a problem too, hence complaints about xyz lens not sharp at xyz focal length. Simple way to test that is use live view
I'll wait until more review for the Pentax turn up, then we can see what the story is with other samples. But it goes without saying you would expect tighter QC on more expensive lenses