1. A method for detecting a face in an unknown input image, comprising the steps of: applying the unknown input image to a first classification tool that determines a rotational angle for rotating the unknown input image to a position that makes the unknown input image most resemble an upright face; rotating the unknown input image by the rotational angle determined by the first classification tool; and applying the rotated unknown input image to a second classification tool which determines whether the rotated unknown input image represents a frontal face.