Telephoto zoom is designed for full-frame Pentax K-mount DSLRs, however can also be used with APS-C models where it provides a 105-315mm equivalent focal length range. Constant f/4 maximum aperture affords consistent brightness throughout the zoom range and offers improved control over depth of field. Multi-layer HD Coating has been applied to individual elements to reduce surface reflections, flare, and ghosting for greater contrast and color fidelity when working in strong lighting conditions. Ring-type Supersonic Direct-drive Motor (SDM) delivers quick, quiet, and precise focusing performance to suit working with moving subjects. A Quick-Shift Focus System also allows for quick switching between AF and MF settings and a two-type focus range limiter helps to quicken focusing times. A moisture-resistant construction benefits this lens' use in inclement conditions, and an SP (Super Protect) coating has also been applied to the front lens element to guard against dust, dirt, and smearing. Rounded nine-blade diaphragm contributes to a pleasing bokeh quality. Electromagnetic diaphragm enables more accurate exposure control during video recording. This mechanism is available only when used in conjunction with K-1 Mark II, K-1, K-3 Mark II, K-3, KP, K-70, K-50, K-S2, and K-S1 cameras.