Some 18th century attempts to reduce it used cemented doublets or triplets, while in 1931 Bernard Schmidt designed a way to reduce it by inserting a slightly wavy glass plate.
For a single element, this phenomenon reaches a minimum when a simple relation between the Coddington shape and position factors holds. The aesthetically displeasing nisen bokeh effect occurs when this phenomenon is overcorrected. Some 18th century attempts to reduce it used cemented doublets or triplets, while in 1931 Bernard Schmidt designed a way to reduce it by inserting a slightly wavy glass plate. Its longitudinal type is the distance between the marginal and paraxial foci(*). Its blur disk goes as the numerical aperture cubed and can thus be reduced by placing a stop against a camera lens. It can also be eliminated for an on-axis object at infinity by using a paraboloid system. For 10 points, name this undesirable optical phenomenon in which there are different foci for rays incident on the center or edge of a lens or mirror, exemplified by elements with a namesake shape.
For a single element, this phenomenon reaches a minimum when a simple relation between the Coddington shape and position factors holds.
spherical aberration