Pentax 21mm F/3.2 AL Limited Lens for Pentax Digital SLR Cameras Equivalent focal length to 31.5mm in the 35mm format with ist D series The image circle is designed to match the CCD used in PENTAX digital SLRs, xceptional high contrast, high resolution optics with minimal aberrations Thin, lightweight design. 4.9 ounces, 5.5 ounces with lens hood Comes with a lens hood to minimize flare and ghost image Responsive "Quick-Shift Focus System" allows instant shift from AF to MF