Aberration

A distortion of image quality or color rendition in a photographic image caused by optical limitations of the lens used for image capture, usually not having all the data from a single point focus in the same plane. Aberrations commonly show up in the form of halation around high-contrast portions of the image, or "smearing" of color toward the edges of the frame. Aspheric lens surfaces and advanced lens coatings are often used in more expensive or complex lenses as a means of reducing aberrations.