Zoom lens and image pickup apparatus having the same

An image pickup apparatus comprising:

• a solid-state image pickup element;
• and
• a zoom lens arranged to form an image of an object on the solid-state image pickup element, wherein
• the zoom lens includes:
• a first lens unit of positive refractive power;
• a second lens unit of negative refractive power;
• a third lens unit of positive refractive power;
• and
• a fourth lens unit of positive refractive power, being disposed in that order from an object side to an image side,
• the second and fourth lens units are moved in a direction parallel with an optical axis of the zoom lens during zooming,
• the first lens unit consists of one negative lens and three or fewer positive lenses, being disposed in that order from the object side to the image side, and
• the following condition is satisfied:
• 25.1<Z×BD1/BD2<4.1×Z,
• where BD1 and BD2 are lengths of the first and second lens units along the optical axis, and Z is a zoom ratio.