Zoom lens and image pickup apparatus having the same

An image pickup apparatus comprising:

• a zoom lens comprising, in order from an object side to an image side, a first lens unit of a positive refractive power, a second lens unit of a negative refractive power, a third lens unit of a positive refractive power, and a fourth lens unit of a positive refractive power,
• wherein in zooming, the first lens unit is configured fixed and the second, third, and fourth lens units are configured movable, and
• wherein the following conditions are satisfied where f3st is a movement amount of the third lens unit associated with zooming from a wide angle end to a telephoto end, f3 is a focal length of the third lens unit, β2w is a lateral magnification of the second lens unit at the wide angle end, and z is a zoom ratio,
• 0.010<(|f3st|/f3)/z<0.045, and
• −0.33<β2w<−0.20;
• and
• an image pickup device configured to receive an image formed by the zoom lens.