To provide a zoom lens system whose aberration including distortion aberration at a wide angle end is completely corrected though it is bright such that its F-number at the wide angle end is ≤3.

The zoom lens system is equipped with, in order from an object side, a first lens group having positive power, a second lens group having negative power, a third lens group having positive power, a fourth lens group having negative power, and a fifth lens group having positive power as a whole and comprising a negative lens element, a positive lens element, a negative lens element and a positive lens element in order from the object side. When varying power from the wide angle end to a telephoto end, at least the first lens group, the third lens group and the fifth lens group are moved to the object side, and the second lens group is moved to an image side.

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