Large fixed aperture, 17mm and Sigma's original Optical Stabilizer
Two FLD (“F” Low Dispersion) glass elements, which have the performance equal to fluorite glass, compensate for color aberration. In addition, two glass mold elements and one hybrid aspherical lens give excellent correction for field curvature and astigmatism. High definition images are ensured throughout the entire zoom range.
The lens is equipped with Sigma’s own unique OS (Optical Stabilizer) function. This system allows the photographer to use shutter speeds approximately 4 stops slower. This ensure you get sharp blurr free images. User can now choose between Pentax camera's SR or activate this OS feature.
The large F2.8 aperture provides a bright viewfinder image, helping the photographer confirm accurate focusing. It is also ideal for emphasizing the subject by creating a natural, blurred background and allowing the use of fast shutter speeds.
The Super Multi-Layer Coating reduces flare and ghosting as well as providing sharp and high contrast images throughout the entire zoom range.
This lens has superior peripheral brightness and provides sharp and high contrast images even at the maximum apertures.
The lens incorporates HSM (Hyper Sonic motor), ensuring fast and quiet AF. HSM is Hyper Sonic Motor, a technology very similar to Pentax's SDM. Note: In order to enjoy this feature, the camera must has Pentax's SDM capability. Camera without SDM can only manual focus using this lens.
This lens has a minimum focusing distance of 28cm throughout the entire zoom range and a maximum magnification ratio of 1:5.
This lens has rounded 7 blade diaphragm which creates an attractive bokeh to the out of focus area of the image.
The inner focusing system eliminates front lens ration, making the lens particularly suitable for using the supplied petal-type hood and circular polarizing filters.
Very solid construction with the typical Sigma EX ("Excellence") finish (crinkle style).