A zoom lens system is used for imaging an object to an image plane. The system, in the order from the object side to the image plane, includes a first lens group with positive refraction power, a second lens group with negative refraction power, a third lens group with positive refraction power, an aperture stop, a fourth lens group with positive refraction power, and a fifth lens group with negative refraction power. The fifth lens group comprises a lens of negative refraction power and a lens of positive refraction power. The system satisfies the formulas: −0.18