Camera vario-lens system of first two positive and third negative groups adjusting individually between maximum and minimum focal moves first and second positive lens groups in unison for focusing.

摘要

The first two positive lens groups (10,20) and the third negative group (30) adjust individually from their shortest focal length to longest focal length along the optical axis in such a way that the distance between first and second groups increases as compared with that between second and third groups which decreases. First and second groups move as one unit for focusing. The design ensures that (KF) lies between 10 and 25. In this (KF) = (fT/fFT)2. (fT) denotes the focal length of the total lens system adjusted to maximum focal length and (fFT) the combined focal length of first and second lens groups adjusted to maximum focal length.