1. A method for generating an x-ray image of an examination subject, comprising the steps of: obtaining a first x-ray image having an image field that contains, and is larger than, a subject image region that contains only an image of an examination subject; digitally processing said first x-ray image to obtain an intermediate image encompassing said image field, said intermediate image being comprised of a plurality of image points each exhibiting a grayscale value; and identifying said subject image region in said intermediate image by designating a grayscale value range, and associating with said subject image region all image points in said intermediate image exhibiting respective grayscale values within said grayscale value range.