04-05-2011, 06:22 AM
[quote name='boren' timestamp='1299415742' post='6553']
I'm considering buying a Tamron 18-250 lens (probably second hand), and as far as I understand most of these lenses suffer from some level of de-centering. For sure I won't purchase a copy that isn't totally free of any signs of de-centering at f/11, but is it reasonable to expect this at f/8.0? If it isn't a pipe dream then this is the benchmark I'm going to set for myself when testing the lens. If it isn't reasonable to expect this, then I may just give up the whole thing.
Thanks!
[/quote]
Yes, it is reasonable that centering should not play a real-life role when stopping down by 1 f-stop.
From a lab perspective you will, of couse, see it beyond in any case but who cares.
I'm considering buying a Tamron 18-250 lens (probably second hand), and as far as I understand most of these lenses suffer from some level of de-centering. For sure I won't purchase a copy that isn't totally free of any signs of de-centering at f/11, but is it reasonable to expect this at f/8.0? If it isn't a pipe dream then this is the benchmark I'm going to set for myself when testing the lens. If it isn't reasonable to expect this, then I may just give up the whole thing.
Thanks!
[/quote]
Yes, it is reasonable that centering should not play a real-life role when stopping down by 1 f-stop.
From a lab perspective you will, of couse, see it beyond in any case but who cares.