Zoom lens and image pickup apparatus including the same

An image pickup apparatus, comprising:

• a zoom lens;
• and
• an image sensor configured to receive an image formed by the zoom lens,
• wherein the zoom lens comprises, 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;
• and
• three or more lens units,
• wherein an interval between adjacent ones of the lens units is changed during zooming,
• wherein an N-th lens unit, where 5≦N holds, counted from the object side has a negative refractive power, and is configured to move to the image side during focusing from infinite object to a close distance object, the N-th lens unit comprising, in order from the object side to the image side, a negative lens, a positive lens, a negative lens, and a positive lens, and
• wherein the following conditional expressions are satisfied:
• −0.15<fN/fT<−0.05;
• and
• −0.30<o1N/dN<0.05,
• where fN represents a focal length of the N-th lens unit, fT represents a focal length of an entire system at a telephoto end, o1N represents a distance from a surface vertex of the N-th lens unit on the object side to a front principal point position of the N-th lens unit, and dN represents a length on an optical axis of the N-th lens unit.