Monochromatic aberration
From The Glossary of Digital Photography
A type of aberration caused by the shape or geometry of the lens. Monochromatic aberration means that a point on the subject, when seen through the lens, is seen as a shape other than a point, such as a blob. All colors or wavelengths of visible light are affected equally. Monochromatic aberration can be broken down into astigmatism, coma, distortion, field curvature, and spherical aberration. See astigmatism; chromatic aberration; coma; distortion; field curvature; spherical aberration
