This chapter describes an initial set of image processing operations and procedures that can be applied to correct some of the defects or shortcomings in as-acquired images that may occur due to imperfect detectors, limitations of the optics, inadequate or nonuniform illumination, or an undesirable viewpoint. It is important to emphasize that these are corrections applied after the image has been digitized and stored, and therefore are unable to deliver the highest quality result that could be achieved by optimizing or correcting the acquisition process in the first place. The corrections are usually applied before enhancement (Chapter 5) and prior to measurements.