Originally posted by luftfluss Where did you find this information? I haven't seen any comparison between those 2 lenses.
Well, ePhotozine had found poor corner sharpness and high chromatic aberration on the DA 18-135mm (
review) especially at longer focal lengths, and sadly, this is consistent with my experience, to the point where it is seldom on my K-3 II (whose 24MP sensor is very picky about glass). The Sigma C 18-200mm (
review) just seems to be much more consistent corner-to-corner with no glaring weaknesses. I know they're tested on different systems, but the difference in optical performance is substantial.
Sigma needs to make more weather-sealed lenses. I know this is a common complaint, but it's just one I can't avoid making here.
I have a feeling I'd still choose the DA 16-85mm over this because it goes down to 16mm, is weather-sealed, and is optically excellent, but the Sigma sure looks like a very tempting alternative...
Originally posted by Nicolas06 To me it look similar to the 18-300 C. You exchange less reach for a bit lighter/smaller/cheaer lense
The Sigma C 18-300mm is actually considerably worse than the 18-200.
Lenstip's review shows poor edge sharpness at longer focal lengths irrespective of aperture typical of superzooms of this kind. The 18-200 is much more balanced. Again, different systems, but the optical performance difference is nontrivial.
---------- Post added 08-22-15 at 10:01 AM ----------
The point is that Sigma's lenses often perform surprisingly well but seem to lack the features we're accustomed to on the Pentax K system. I'd love to have some of these new Sigma Global Vision lenses, but weather sealing just seems to be too essential of a feature for us Pentax users.
I'm not here to bash any particular lens manufacturer, but I really think Sigma would gain more adoption if they had more sealed lenses.
—DragonLord