ABSTRACT
After photography was invented in 1839, there was a pressing need for lenses that could produce sharp, undistorted images with wide fields of view. This chapter considers why multi-element lenses are necessary in order to minimize aberrations while providing large apertures. It also finds that multi-element lenses give unacceptable light transmission, ghosts, and flare in the absence of antireflective multi-coating. The great lens designer Rudolf Kingslake said, "The design of any photographic lens is dominated by a certain mathematical expression known as the Petzval sum". He was referring to the specification of the image curvature that is produced by any simple or compound lens. This curvature is such an obvious characteristic of a simple lens that some opticians do not even regard it as an aberration. Most modern lenses contain autofocus mechanisms and in some cases vibration isolation systems based on the movement of a lens element to counteract low frequency vibrations.
