Aberrations of long focus anastigmatic photographic objectives

Aberrations of long focus anastigmatic photographic objectives

Author: Bennett, A.H.

Year: 1924

No lens system gives perfect definition because of the inherent aberrations of spherical refracting surfaces. The aberrations of a centred lens system are denned, and the characteristic manner in which each aberration affects the image is discussed. Methods for the determination of the various aberrations of a photographic objective are described. The Hartmann method, for which a special camera was designed, was used for the measurement of spherical aberration and departure from the sine condition, while a lens-bench method was employed in the measurement of curvature of field, astigmatism, distortion, and lateral and axial chromatism. The aberrations of thirty-three photographic objectives of the anastigmatic type, made by different manufacturers, are presented graphically. The variation among individual lenses from the same manufacturer as well as differences found in lenses of the same construction, but by different manufacturers, are discussed.