Zoom lens and image pickup apparatus

A zoom lens, comprising:

• a first lens group having a positive refracting power and 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;
• and
• a third lens group having a positive refracting power and positioned at a fixed position;
• the first, second and third lens groups being disposed in order from the object side to the image side;
• two thirds or more lenses from among a number of lenses which configure the first to third lens groups being formed from a resin material;
• the zoom lens satisfying the following conditional expressions (1) and (2):
• 4.0<ft/fw (1)
• −100.0<f(1 to 3)/fw<−6.4 (2)
• where fw is a focal length of the entire lens system in a wide angle end state, ft a focal length of the entire lens system in a telephoto end state, and f(1 to 3) is a combined focal length of the first to third lens groups at all zoom positions,
• wherein a fourth lens group has a positive refracting power and is movable in the direction of the optical axis for correction of a focal position and for focusing by zooming and the fourth lens group is disposed on the image side of the third lens group,
• wherein the fourth lens group is configured from a positive lens having a positive refracting power and a negative lens having a negative refracting power, which are disposed in order from the object side to the image side, and
• one of the positive lens and negative lens is formed from a glass material and the other one of the lenses is formed from a resin material.

An image pickup apparatus, comprising:

• a zoom lens;
• and
• an image pickup device for converting 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 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 positioned at a fixed position, and
• a fourth lens group movable in the direction of the optical axis and being disposed on the image side of the third lens group, the fourth lens group configured from a positive lens having a positive refracting power and a negative lens having a negative refracting power, the positive lens and the negative lens being disposed in this order from the object side to the image side,
• the first, second and third lens groups being disposed in order from the object side to the image side,
• two thirds or more lenses from among a number of lenses which configure the first to third lens groups being formed from a resin material,
• one of the positive lens and negative lens, in the fourth lens group, is formed from a glass material and the other one of the lenses is formed from a resin material;
• the zoom lens satisfying the following conditional expressions (1) and (2):
• 4.0<ft/fw (1)
• −100.0<f(1 to 3)/fw<−6.4 (2)
• where fw is a focal length of the entire lens system in a wide angle end state, ft a focal length of the entire lens system in a telephoto end state, and f(1 to 3) is a combined focal length of the first to third lens groups at all zoom positions.