A zoom lens system is disclosed which comprises in order from an object
side to an image side: a first lens unit with a positive optical power
(inverse of the focal length), a second lens unit with a negative optical
power; and one or more lens units; and with which at least one of the
first lens unit and the second lens unit is moved during zooming. By
specifying the optical characteristics (shape, material, focal length,
etc.) of the lens elements making up the second lens unit in the zoom
lens system, a high zoom ratio is obtained with a simple arrangement, and
an optical system, which can adequately accommodate even the use of a
solid-state image pickup element with a large number of pixels, is
realized.