1. A method of tracking a face in a reference image stream, comprising: using a digital image acquisition device including an imaging optical system, and a processor, for obtaining meta-data to apply to a further action, wherein the method includes: acquiring a full resolution main image and an image stream of relatively low resolution reference images each including one or more face regions; identifying one or more face regions within two or more of said reference images; determining a relative movement between said two or more reference images; determining a size and location of said one or more face regions within each of said two or more reference images; applying concentrated face detection to at least a portion of said full resolution main image in a predicted location for candidate face regions having a predicted size as a function of the determined relative movement and the size and location of said one or more face regions within said reference images, to provide a set of candidate face regions for said main image; and applying meta-data of one or more of the set of candidate face regions to a further action.