This invention relates to a four-group-lens zoom lens which is small in size and has a high magnification changing rate of which zoom ratio is 4. The zoom lens comprises a magnification changing system in which a first group, a second group and a third group have positive, negative and positive refractive powers, respectively, and a fourth group in the form of a relay lens. It is advantageous to make the focal length of lenses in the first group small in order to miniaturize the magnification changing system. In addition, it is advantageous that the relay lens be made small in the focal length and made small in telephone ratio, in order to miniaturize the whole zoom lens. In order to make the telephoto ratio small, it is advantageous to divide the fourth group lens into the front group and rear group to impart a positive refractive power to the front group and a negative refractive power to the rear group but a difficulty occurs in correction of aberrations, and therefore, a positive refractive power is imparted even to the rear group.
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