The Pentax FA 645 120mm f/4 SMC Macro Lens is a medium format, manual and autofocusing, short telephoto / portrait prime lens that provides a 35mm equivalent focal length of 96mm. Features include: floating and an independently-moving aperture mechanism; Maximum aperture of f/4; 1:1 magnification ratio; Minimum focus distance of 15.4 inches; a Super Multi Coating (SMC) to significantly increase the amount of light transmission; Extra-low Dispersion (ED) glass to corrects chromatic aberration; a focus limiter to set the focusing range for increased AF speed.