Optical distortion: also known as distortion. Due to the difffferent magnififications of each fifield of view of the lens, the image loses similarity to the object. This kind of image distortion defect is called optical distortion. Optical distortion only affffects the geometry of the image, and does not affffect the sharpness of the image. There are two main types of common optical distortion, barrel distortion and pincushion distortion, as shown in the fifigure.