1. A method of image subtraction comprising the steps of: a. taking a series of frames of a subject using a video camera such that each frame will contain an even field of raster lines and an odd field of raster lines; b. illuminating the subject in a manner so that illumination is alternately on then off for successive fields to create at least one frame in which one of the even field of raster lines and the odd field of raster lines was created with the illumination off and the other of the even field of raster lines and an odd field of raster lines was created with the illumination on; c. grabbing a single frame in which one of the even field of raster lines and the odd field of raster lines was created with the illumination off and the other of the even field of raster lines and the odd field of raster lines was created with the illumination on; and d. finding an absolute difference between the odd field and the even field in said single frame thereby creating a representation of the subject illuminated by system illumination without ambient illumination.