| 摘要 |
A zoom lens system having two, positive and negative, lens units, which is designed so that the number of constituent lenses is minimized to lower the cost and reduce the size, and yet high performance is realized, and that deterioration of the performance caused when the lenses are incorporated into a lens frame is minimized, and assembling is also facilitated. The zoom lens system has a 1-st lens unit (G1) of positive power and a 2-nd lens unit (G2) of negative power and is adapted to effect zooming by varying the spacing between the 1-st and 2-nd lens units (G1 and G2). The 1-st lens unit (G1) includes a single cemented lens (L12) composed of a negative lens (L1) and a positive lens (L2). The 1-st lens unit (G1) has at least one aspherical lens surface and satisfies the condition of nu P- nu N>15, where nu N is the Abbe's number of the negative lens (L1), and nu P is the Abbe's number of the positive lens (L2).
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