Abstract: The improved zoom lens system comprises, in order from the object side, a positive first lens group, a positive second lens group and a negative third lens group, the second lens group consisting of a single positive lens group that has aspheric surfaces on both surfaces closest to the object and closest to the image, and all of the first, second and third lens groups are moved towards the object during a zoom from the wide-angle end to the narrow-angle end, the lens system further satisfying specific conditions.This zoom lens system is capable of exhibiting a zoom ratio of at least 2.5 using 4 or 5 lens elements and has an F number of about 1:4-8 to make itself practical for use with still cameras.

Abstract: An improved zoom lens system is disclosed which includes at least three lens groups which are arranged, in order from the object side, as a first lens group having a positive focal length, a second lens group having a positive focal length and a third lens group having a negative focal length. When zooming is carried out from the wide-angle to the narrow-angle end, the first, second and third lens groups are all moved towards the object so that the distance between the first and second lens groups is increased whereas the distance between the second and third lens groups is decreased. The system is characterized in that the second lens group has at least two aspheric surfaces.