1. A portable digital image acquisition device, comprising: (a) at least one lens and at least one sensor for acquiring a main digital image and first and second reference images of approximately a same acquired scene that includes one or more luminous objects; (b) a memory for storing the main digital image; (c) one or more non-transitory processor-readable media having digital code embedded therein for programming a processor to perform a method of determining an iris region of an eye in the main digital image using the first and second reference images, wherein the method comprises: (i) acquiring the first and second reference images using the at least one lens and the at least one sensor; (ii) normalizing the first and second images to generate normalized first and second reference images; (iii) analyzing one or more differences between the first and second normalized reference images; (iv) determining the iris region of the eye within the main image based on the analyzing; (v) generating meta data based on the determining of the iris region; and (vi) storing, transmitting, communicating, displaying, or projecting the main image or a further processed version, or combinations thereof, along with said meta data.