Zoom lens and image pickup apparatus having the same

A zoom lens comprising, in order from an object side to an image side:

• a first lens unit having a positive refractive power;
• a second lens unit having a negative refractive power;
• a third lens unit having a positive refractive power;
• and
• a rear lens group including at least one lens unit,
• wherein an interval between each pair of adjacent lens units is changed during zooming,
• wherein the zoom lens further comprises an aperture stop,
• wherein a lens unit arranged on the image side of the aperture stop is configured to move during zooming,
• wherein the first lens unit consists of at least two positive lenses, and two negative lenses, and
• wherein the following conditional expressions are satisfied:
• −0.0040≤(θCtnave−θCtpave)/(vdnave−vdpave)≤0.0040;
• 30.0≤vdnave≤60.0;
• 0.10≤vdnmax/vdpmin≤1.00;
• −7.72≤f1/f2≤−4.2;
• and
• 0.5≤TD/ft≤0.844,
• where θCtnave represents an average value of partial dispersion ratios of materials of the two negative lenses, θCtpave represents an average value of partial dispersion ratios of materials of two positive lenses having the highest refractive powers of the at least two positive lenses, vdnave represents an average value of Abbe numbers of the materials of the two negative lenses, vdpave represents an average value of Abbe numbers of the materials of the two positive lenses, vdnmax represents larger one of the Abbe numbers of the materials of the two negative lenses, vdpmin represents smaller one of the Abbe numbers of the materials of the two positive lenses, f1 and f2 represent focal lengths of the first lens unit and the second lens unit, respectively, TD represents a distance from an optical surface closest to the object side to an image plane, and ft represents a focal length of the zoom lens at a telephoto end.