Aware of the limitations of optical variable focal objectives compared to fixed targets, but absolutely trying to lighten my pack, I seek a versatile and almost universal goal for portraiture, architectural photography but also photographed scenes street, landscapes, flowers in macro ... The zoom Pentax 12-135 f: 3.5-5.6 sold in kit with the K3 is great, but I wanted a wider choice of focal lengths: where purchasing the Sigma 12-250 f: 3.5-6.3. I thought the comparison of the two objectives might interest those who are asking the same questions ... The two objectives are excellent choices and excellent qualities if we accept the "limitations" zooming compared to fixed focal lengths that are expensive if you multiply them! Both zooms offer equivalent performance in terms of maximum aperture (f 3.5) and substantially equivalent dimensions in terms of size and weight, though, and it's normal for the extent of focal lengths, the Sigma is slightly longer, wider and heavier, the pledged the Sigma K3 is taken under control (but worse than the Pentax). From the standpoint of construction and mechanics, in both cases, it's serious and solid, but let's be clear, the Pentax (WR / Water resistant, tropicalized, etc ...) dominates his rival and looks even better adjusted, stronger, etc ... From a mechanical point of view, the same conclusion: the ideal and pleasing smoothness of the ring of Pentax zoom far surpasses that of maneuver Sigma which, moreover - without doubt this is voluntary? - Already a little hard for short focal lengths, forces frankly "force" for long lenses that require the implementation of a second "floor" in the extension of the goal. AF is also more flexible, faster and completely silent on the Pentax: Sigma on, it generates some "rattling" and seems less fluid. All this therefore gives a fairly clear advantage to Pentax ... but the rest remains: wider choice of focal lengths, possibility of macros with a very low minimum MAP, an optical quality that seems higher on the first test in terms of sharpness (though ...), distortion ... to restore Sigma its purpose. The choice will be based on real needs in terms of telephoto (375 against 205 in 35mm equivalence), macro ... In between, my heart is torn ...
