Featuring HD and Aero Bright Coatings to optimize light transmittance and minimize reflections, this medium telephoto lens offers a focal length of approximately 71mm (or approximately 56mm when mounted on a PENTAX 645 film-format camera body) in the 35mm format. By incorporating two ED (extra-low dispersion) elements and one glass-molded aspherical element in its optics, it assures high-resolution image reproduction over the entire image field, while effectively minimizing chromatic aberration, a problem commonly associated with fast lenses. This is the first lens to incorporate the PENTAX-innovated SR (Shake Reduction) mechanism within the lens barrel. This mechanism effectively compensates for camera shake up to approximately 3.5 shutter steps, assuring sharp, blur-free images even under conditions prone to camera shake, such as when handholding the camera in poorly lit locations without flash illumination, or when photographing sunset scenes.