Modern Lens Design, 2nd Edition

Chapter 14Reversed Telephoto (Retrofocus and Fish-Eye) Lenses

14.1 The Reversed Telephoto Principle

The reversed telephoto camera lens probably had its origin when the three-film Technicolor movie camera required a long enough back focus to accommodate the color separation prism cube. When a negative lens is placed at the front focal point of a camera lens, the back focus is lengthened, but the effective focal length is unchanged. So the early Technicolor efforts simply put a negative achromat out in front of a standard camera lens to make room for the prism. Eventually the potential of a unified design was recognized, and the reversed telephoto came into its own as a major design type. It is an excellent form, achieving good aberration correction, ...