<p>If size isn't a priority, I'd go with 16-85. I find the results from the 18-135 to be perfectly usable, and the 20-40 better IQ. I guess I don't care much about corners, as I've never noticed them being problematic. I had a 16-50 for a while, and while it had to go back for an unrelated issue, I wasn't that impressed that the IQ was any better than the 20-40, and possibly worse. I prefer small size, so I will stick with the DA limited zoom. But it would be tempting to get the wider range of the 16-85 if IQ was about the same.</p>