Curvature of field and distortion refer to the location of image points with respect to one another. Even though the former three aberrations may be corrected for in the design of a lens, these two aberrations could remain. In curvature of field, the image of…

Field curvaturelens

Curvature of field is present when the sharpest image is formed not on a flat plane but on a curved surface. Astigmatism occurs when the lens fails to focus image lines running in different directions in the same plane; in a picture of a rail…