This unique pancake-style standard lens measures less than a half inch in length and weighs just 1.8 ounces. Offering incredible sharpness and image quality, this lens is ideal for even the most discerning photographer who demands top performance in an ultra-compact package. Features APS-C Fomat. Ultra low profile is only 0.36 inches thin at 1.8 oz. Short 16 inch minimum focus distance. Nine rounded aperture blades produce extraordinarily smooth, natural bokeh. PENTAX KAF mount is compatible with current and past K-mount compatible cameras. Aesthetic design by world famous designer Marc Newson. Fixed focal length 40mm prime lens is equivalent to 61mm in the 35mm format. Maximum F2.8 aperture is ideal for existing light photography and creative depth of field applications. PENTAX SP (Super Protect) coating on lens surface helps repel elements and aids in cleaning.