I mounted it on my Pentax 16-45 mm K-5, I am satisfied with the rendering of the lens, the sharpness is good even at full aperture. I wanted a transtandard zoom with a wide angle focal length of the Pentax brand at a price "affordable" and constantly opening. I do not put it 5 stars because I would have preferred to have the 16 mm with the barrel of undeployed zoom that casts a shadow on the bottom of the picture with the use of built-in flash, ie you can not use this flash of 16-19 mm, no gray problem scope from 20 mm with the Pentax K-5 and of course without visor, you have a cobra type flash ... but this "problem" with flash of shadow is the lot of many wide-angle zoom lenses, so doing 16-45 is no less well than others on this subject. There are also some chromatic aberrations that are easily corrected in post-processing. The objective is of good quality, the zoom ring is flexible to use. What also interested me much in my choice was the focal length of 16 mm focal handy when you lack perspective. The 45 mm are a bit tight for the portrait (in any case for the portrait, nothing beats a fixed focus wide opening), I end by saying that it is still versatile zoom well for reportage / landscape with its range. Sincerely.
