1. A method for obtaining a range image using depth from focal gradient analysis, the method including: acquiring a near reflectance image; using a focus operator to obtain a near focal image; acquiring a farther reflectance image; using a focus operator to obtain a farther focal image; warping the farther focal image so as to decrease correspondence error of the farther focal image with respect to the near focal image, thereby providing a warped farther focal image; and range normalizing the near focal image and the warped farther focal image so as to provide a range image.