Distortion
From The Glossary of Digital Photography
A type of monochromatic lens aberration. Distortion occurs when straight lines are bent after going through the lens. There are two types of distortion: barrel distortion and pincushion distortion, depending on which direction the lines bend. These types of distortion are usually easy to correct in lenses of normal focal lengths by using multiple element lens designs. See also aberration; barrel distortion; pincushion distortion
