Patent ID: 8780453

Claim:
A zoom lens comprising, in order from the object side, a first lens unit having a positive refractive power which does not move for varying magnification, a second lens unit having a negative refractive power which moves for varying magnification, a third lens unit having a negative refractive power which moves for varying magnification, and a fourth lens unit having a positive refractive power which does not move for varying magnification, wherein the first lens unit includes a positive lens which satisfies the following conditions: 70 <νp< 85, 2.31 <Np+ 0.01 ×νp< 2.58, and 1.6 <Np< 1.85, where Np is a refractive index of the positive lens, and νp is an Abbe constant of the positive lens, and wherein the following condition is satisfied: 1.25 <|fp/fna|< 1.7, where fp is a focal length of the positive lens, wherein the first lens unit includes a plurality of negative lenses and fna is a combined focal length of negative lenses in the first lens unit defined by the following equation: fna = 1 ∑ i = 1 n ⁢ 1 fn i where n is a number of the negative lenses included in the first lens unit, and fni is a focal length of the i-th negative lens.