Pentax DA 40mm f/2.8 XS Lens Designed by Marc Newson and with a profile that is .36 inches thin at 1.8oz 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 coating protects the exposed lens elements Pentax KAF mount is compatible with current and past K mount compatible cameras