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 third lens unit includes at least two negative lenses and at least three positive lenses, and
• wherein the following conditions are satisfied:
• −0.0030≤(θCtnave−θCtpave)/(vdnave−vdpave)≤0.0040;
• 30.0≤vdnave≤75.0;
• and
• 0.3≤BF/fw≤3.0,
• where θCtnave represents an average value of partial dispersion ratios of materials of two negative lenses having the strongest refractive powers of the at least two negative lenses, θCtpave represents an average value of partial dispersion ratios of materials of three positive lenses having the strongest refractive powers of the at least three 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 three positive lenses, BF represents a back focus, and fw represents a focal length of the zoom lens at a wide angle end.