A zoom image pickup optical system including, in order from the object
side, a first lens unit having positive refractive power, a second lens
unit having negative refractive power, a third lens unit having positive
refractive power and a fourth lens unit having positive refractive power,
in which at least the second lens unit and the fourth lens units are moved
along an optical axis to change a magnification, in which the third lens
unit includes at least two lens components, in which the fourth lens unit
includes at least two lens components, and in which radii of curvature on
at least one of pairs of surfaces of the third lens unit and the fourth
lens unit such as an image side surface of a most image side lens
component in the third lens unit and an object side surface of a most
object side lens component in the fourth lens unit which correspond to
each other with regard to an airspace between the third lens unit and the
fourth lens unit have different signs.
