Zoom lens and image pickup apparatus

An image pickup apparatus, comprising:

• a zoom lens;
• and
• an image pickup device configured to convert an optical image formed by the zoom lens into an electric signal;
• the zoom lens including
• a first lens group having a positive refracting power and normally positioned at a fixed position,
• a second lens group having a negative refracting power and movable in a direction of an optical axis for zooming,
• a third lens group having a positive refracting power, and
• a fourth lens group movable in the direction of the optical axis for correction of a focal position by zooming and for focusing;
• the first, second, third and fourth lens groups being disposed in order from the object side to the image side;
• the first lens group comprising three lenses including a negative lens, a positive lens and another positive lens disposed in order from the object side to the image side and satisfying the following conditional expressions (1), (2) and (3)
• 15.0<ft/fw<31.0 (1)
• 7.0<f1/fw<13.0 (2)
• −8.5<fL1/fw<−4.0 (3)
• where fw is the focal length of the entire lens system in a wide angle end state, ft is the focal length of the entire lens system in a telephoto end state, f1 is the focal length of the first lens group, and fL1 is the focal length of the negative lens of the first lens group.

A zoom lens, comprising:

• a first lens group having a positive refracting power and normally positioned at a fixed position;
• a second lens group having a negative refracting power and movable in the direction of an optical axis for zooming;
• a third lens group having a positive refracting power;
• a fourth lens group having a positive refracting power, which is movable in the direction of the optical axis for correction of a focal position by zooming and for focusing;
• and
• a fifth lens group having a positive refractive power and disposed on the image side of the fourth lens group,
• the first, second, third, fourth and fifth lens groups being disposed in order from the object side to the image side;
• the first lens group comprising three lenses including a negative lens, a positive lens and another positive lens disposed in order from the object side to the image side and satisfying the following conditional expressions (1), (2) and (3)
• 15.0<ft/fw<31.0 (1)
• 7.0<f1/fw<13.0 (2)
• −8.5<fL1/fw<−4.0 (3)
• where fw is the focal length of the entire lens system in a wide angle end state, ft is the focal length of the entire lens system in a telephoto end state, f1 is the focal length of the first lens group, and fL1 is the focal length of the negative lens of the first lens group.