1. A method of comparing a three-dimensional facial image with a two-dimensional intensity image of a face comprising the steps of: providing a filter having three orthogonal components derived from a plurality of normal vectors derived from points defining the surface of the three-dimensional facial image; performing a correlation by the steps of providing a transform of at least one of the two-dimensional intensity image other than a transform of the intensity image into a three-dimensional image and filtering the provided transform using the filter derived from three-dimensional facial image to obtain correlation results which are partially independent of the angle from which a face within the two-dimensional intensity image is illuminated; and, when the correlation results are within a first range, providing a signal indicative of a match.