For a super zoom this lens controls aberrations extremely well. It takes some extreme situations to get fringing or flare to truly mess up your images.
Except in the corners, which are generally going to be soft to begin with, fringing is minimal. At 270mm it can easily be seen, though it barely protrudes beyond edges, even in bright conditions.
270mm F6.3 (wide-open): 100% crop
At the wide end fringing can also be observed, but it is once again mild.
18mm F3.5 (wide-open): 100% crop
This lens is not terribly prone to flare. We had to shoot into the sun to provoke flare and it then it only showed at the wide end as the following examples show. We shot with a K-5 at ISO 200. Click on an image to browse larger versions. The three last shots were shot with the lens stopped down about two stops. At 115mm and 270mm we got the same results with the lens fully open.
|18mm F3.5 (wide open): flare/internal reflection when overexposing|
|18mm F6.7 (two stops down): some flare|
|115mm F11 (two stops down): no flare|
|270mm F11 (about two stops down): no flare|
The first two sample photos are also good examples of what you can expect on a daily basis in terms of vignetting and distortion.