Lens system having variable magnification

摘要

A lens or a lens system of variable magnification is described having exchangeable lens groups, which comprises from front to rear a first lens group of positive refractive power, a second lens group of negative refractive power, and a third lens group of positive refractive power. The focal length of the total system can be varied by exchanging the second lens group for a further lens group which has a refractive power differing from the refractive power of the second lens group, and by simultaneous displacement of the first lens group.