Large F2.8 maximum aperture Despite its compact dimensions, this ultra-wide-angle zoom lens provides a focal length of 11 to 18 millimeters (equivalent to 17mm to 27.5mm in 35mm format) to produce magnificent, dynamic images. Since its maximum aperture is fixed at F2.8 over the entire zoom range, it delivers sharp, bright images of scenes with starry skies. Thanks to a minimum focusing distance of 0.3 meters, the lens also lets the photographer capture true-to-life close-up images by emphasizing the depth of field with an effectively defocused background. HD Coating to enhance imaging power This lens features high-grade, multi-layer HD Coating,* which reduces the average reflectance in the visible ray spectrum to less than 50% of conventional multi-layer coatings. It effectively minimizes flare and ghost images even in demanding lighting conditions such as backlighting. Ideal design optimized for photography of landscapes and star-lit scenes The unique Focus Clamp Mechanism allows the photographer to lock the lens’s focal point, even when the focus ring is rotated. This improves the lens’s operability in photographing such subjects as landscapes and star-lit scenes, which demand high-precision focusing during extended exposures. It also has special features for improved operability and versatility in outdoor shooting, such as a space for wrapping heating wires around the lens barrel to prevent dew condensation, without affecting focus-ring operation; and a metallic frame structure to more effectively transmit the heat of the heating device to the lens. Dustproof, weather-resistant construction Developed as an AW (All Weather) model, this zoom lens features a dustproof, weather-resistant construction to prevent the intrusion of water and dust particles into the lens interior. By pairing it with a PENTAX weather-resistant digital SLR camera body, this assures a highly durable, reliable digital imaging system that performs superbly in demanding shooting settings — even in rain or mist, or at locations prone to water splashes. Other features - Smooth, quiet AF operation using a DC motor - Round-shaped, nine-blade diaphragm to produce a natural, beautiful bokeh (defocus) effect while minimizing the streaking effect of point light sources - Quick-Shift Focus System to provide an instant shift to manual-focus operation after locking the subject in focus during AF operation by pressing the shutter-release button halfway down; usable at any time during AF operation - SP (Super Protect) Coating to keep the lens’s front surface free of dust and stains