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 negative refractive power, the first lens unit being disposed closest to the object side;
• a second lens unit having a negative refractive power, the second lens unit being disposed adjacent to the first lens unit;
• a stop, the stop being disposed adjacent to the second lens unit;
• a third lens unit having a positive refractive power, the third lens unit being disposed adjacent to the stop;
• and
• a fourth lens unit having a positive refractive power, the fourth lens unit being disposed adjacent to the third lens unit,
• wherein the distance between the first lens unit and the second lens unit changes during zooming,
• at least one of the second, third, and fourth lens units moves so that the distance between the second lens unit and the third lens unit at the telephoto end is smaller than that at the wide-angle end and so that the distance between the third lens unit and the fourth lens unit at the telephoto end is larger than that at the wide-angle end, and
• the distance between the stop and the third lens unit changes during zooming.