The DA 18-135mm is a very useful, versatile lens, and capable of quality imaging. It is at its best between 18-70mm, where it can also maintain f/3.5-4.5 apertures wide open, which is better for low-light or action shots needing a higher shutter speed than an aperture of f/5.6 would be. It can do this because it is still only at about half of its zoom range. Edge and corner quality are compromised mainly at the longer end of its zoom range, though frequently this is not noticed because in longer tele shots the central portion usually becomes the most important part of the shot anyway.
I have other, fine quality lenses costing much more, but I value the DA 18-135mm for its very useful zoom range and its high image quality. In addition to its very good WR construction, it also has one of the fastest, quietest, and surest AF performances of any lens put on a Pentax DSLR.
Last edited by mikesbike; 11-07-2017 at 04:44 PM.