1. A method of tracking faces in an image stream with a digital image acquisition device, comprising: a. receiving an acquired image from an image stream including one or more face regions; b. sub-sampling said acquired image at a specified resolution to provide a sub-sampled image; c. calculating a corresponding integral image for a least a portion of said sub-sampled image; d. applying face detection to at least a portion of said integral image to provide a set of one or more candidate face regions; e. adjusting a resolution for sub-sampling a next acquired image; f. repeating a. to e. at the adjusted resolution periodically on a selected plurality of images of an image stream including a main acquired image chronologically following a plurality of images of said selected plurality of images.