A system and related method for acquiring high quality images of the iris of an unconstrained subject comprising a camera; a controllable focusing component; a focus controller component that controls the lens to focus at successively different points within a focus range, such focus control performed without any input from measurement of whether the image is in focus or out of focus, be it based from measurements of the image or other distance metrics to the subject; and a sharpness detection component that rejects the most out-of-focus images based on measurement of focus on the image is disclosed.