The Sigma 18-35mm f/1.8 DC HSM Lens for Pentax is a wide-angle tonormal-length zoom lens that features a fast, bright constant f/1.8maximum aperture. It is specifically designed for use with APS-C-sizedsensors and provides a 35mm-equivalent focal length range of 27-52.5mm.
The lens integrates four aspherical elements into its construction aswell as five Special Low Dispersion (SLD) glass elements to helpminimize various aberrations and distortions throughout the zoom rangeas well as provide greater image sharpness and clarity. A Super Multi-Layer Coating has also been applied to lens elements to reducesurface reflections, lens flare, and ghosting to produce images withhigher contrast and color fidelity. The lens barrel design isconstructed from a Thermally Stable Composite (TSC) material that isakin to metal in texture and resistance to temperature and environmentalchanges while also remaining lightweight and compact. An internalfocusing and zooming mechanism also helps to maintain a compact andconsistent overall length and non-rotating front ring also better enables the use of circular polarizing filters. For control of focus, aHyper Sonic Motor (HSM) is used to ensure fast, precise, and quietfocusing capabilities that are well suited to continuous shooting andmovie recording.
