Aperture - a disadvantage? Yes, increase the ISO to 400 - 800 and the problems are solved! On K-5 with this lens, I shot a seascape with a quality of 3 stars. Without any photoshop, I took a photo of 30 by 45: the quality is fabulous. And the soul required tests, and then the professional laboratory took the same photo sized 50 by 70. And the quality is super again! For a long time he cursed himself, because I bought 16-50 / 2.8 the day before receiving the photo (oh, and a heavy bastard!). And now, for trips, the soul asks for 18 - 135. But is it necessary - is it?