1. A system for acquiring imagery in a large capture volume, acquiring a series of images of a subject at a predetermined range of focus values, independent of feedback from a focus measurement value, the series of images including high quality images of an iris of an unconstrained subject, the system comprising: a camera; a lens with controllable focus; a focus controller component comprising a processor that controls the lens to focus at a predetermined series of different points within a focus range, without any input from measurement of whether the image is in focus or out of focus, or other distance metrics to the subject; and a sharpness and/or contrast detection component comprising a processor that rejects the most out-of-focus images based on measurement of focus on each of the acquired images.