All points are fair, and each owner needs to evaluate what it takes to make a lens do well enough for their needs. I have tried three of the 18-135s and it doesn't work for me. I sold my most-recent copy and picked up a Sigma 18-250mm the same afternoon, and put some money in the bank (aka 'lens fund'). The compromises required for this lens fit me better, and it's that simple.
I will post some teeny images here to show what I mean, but click 'em to see things better.
|hmm, wires look|
|250mm f/8 bottom crop 100% - soft w/minimal fringing. |
The extreme corners do show more fringing.
And lest we forget, the Sigma can do closeups to 1:2.5, almost half life-size. I tested it against my Pentax A50/2.8 macro and 1:2.5 is a very good match for scale, but let's be clear the macro prime impressively outscores the superzoom. When closeups matter the 50 must come along, but when it's incidental to the shooting this zoom will serve well enough in good light. Funny thing about closeup ratings, Sigma always underrates their zooms: from the 17-70 to the old 18-200 to this one, I can always squeeze out a closer closeup than they claim. How nice!