Patent ID: 7599123

Claim:
A zoom lens system comprising, in order from an object side: a first lens group having negative refractive power; a second lens group having positive refractive power; a third lens group having negative refractive power; and a fourth lens group having positive refractive power; upon varying a focal length from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group decreasing, a distance between the second lens group and the third lens group increasing, and a distance between the third lens group and the fourth lens group decreasing; the second lens group consisting of two positive lenses or less and one negative lens; the fourth lens group consisting of two positive lenses or less and one negative lens; the following conditional expressions being satisfied: 25≦νd2n≦40 when 25≦νd2n≦30 −0.035×ν d 2 n+ 2.63≦ nd 2 n≦ 1.79 when 30<νd2n≦35 1.58<nd2n≦1.79 when 35<νd2n≦40 1.58 <nd 2 n≦− 0.034×ν d 2 n+ 2.98 where νd2n denotes Abbe number of the negative lens in the second lens group at d-line, which has a wavelength λ=587.6 nm, and nd2n denotes a refractive index of the negative lens in the second lens group at d-line; and the following conditional expressions being satisfied: 25≦νd4n≦40 when 25≦νd4n≦30 −0.035 ×νd 4 n+ 2.63≦ nd 4 n≦ 1.79 when 30<νd4n≦35 1.58<nd4n≦1.79 when 35<νd4n≦40 1.58 <nd 4 n≦ 0.034 ×νd 4 n+ 2.98 where vd4n denotes Abbe number of the negative lens in the fourth lens group at d-line, and nd4n denotes a refractive index of the negative lens in the fourth lens group at d-line.