| 摘要 |
Providing a zoom lens system being inexpensive, compact and lightweight with high optical performance, and an imaging apparatus, and a method for varying a focal length. The zoom lens system includes, in order from an object, 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 zooming from a wide-angle end state to a telephoto end state, a distance between the first and second lens groups decreases, a distance between the second and third lens groups increases, and a distance between the third and fourth lens groups decreases. The second lens group consists of two positive lenses or less and one negative lens. The fourth lens group consists of two positive lenses or less and one negative lens. Given conditions are satisfied.
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