Yet another variety has barrel and pincushion arrays, which are alternate forms of a square grid of lines.  
One type of this property is characterized by the presence of a parabaloidal surface known as the Petzval surface, while another type is typified by a phenomenon known as the circle of least confusion.  Yet another variety has barrel and pincushion arrays, which are alternate forms of a square grid of lines.  Of the six types, the least common is coma, which results in a comet-shaped picture.  Curvature of field, spherical, and chromatic are just some of the types of, FTP, what optical property defined as the deviation of light rays through lenses causing a blurred image?
One type of this property is characterized by the presence of a parabaloidal surface known as the Petzval surface, while another type is typified by a phenomenon known as the circle of least confusion.  
aberration