? The DA-Series features a responsive "Quick-Shift Focus System" that allows photographers to instantly switch the focus mode from auto to manual with a slight twist of the focus ring. Coupled with a simple, functional design and the elimination of an aperture ring, this new mechanism considerably improves the camera's operability. The lens also incorporates an Extra-low Dispersion (ED) glass lens element and two aspherical lens elements for true-to-life image reproduction and overall size reduction. The image circle in DA-series lenses, including the smc PENTAX-DA 16mm-45mm f/4 ED AL, is designed to perfectly match the 23.5mm x 15.7mm size of the CCD used in PENTAX digital SLRs to optimize camera performance. The new design also contributes to a drastic reduction in size, weight and production cost, compared to 35mm-format counterparts with similar specifications.