Compact zoom lens

A zoom lens comprising, from front to rear, a first lens group of negative refractive power, a second lens group of positive refractive power and third lens group including a positive lens and a negative lens in this order from the front and whose overall refractive power is negative, and zooming from the wide-angle end to the telephoto end is performed by moving each of said first, second and third lens groups forward, wherein said third lens group moves at a higher speed than said second lens group, and focusing is performed by moving said third lens group, wherein the zoom lens satisfies the following conditions:

• 1<f31/.vertline.f3.vertline.<2
• N31<N32
• 1<RIII2/RIII3<2
• (RIII2<0, RIII3<0)
• where f3 and f31 are focal lengths of said third lens group and said positive lens respectively;
• N31 and N32 are refractive indices of materials and of said positive lens and said negative lens respectively, and RIIIi is a radius of curvature of the i-th lens surface counting from front in said third lens group.

A zoom lens comprising, from front to rear, a first lens group of negative refractive power, a second lens group of positive refractive power and a third lens group of negative refractive power, zooming from the wide-angle end to the telephoto end being performed by moving said first, second and third lens groups each forward, and said zoom lens satisfying the following conditions:

• 1. 0<.vertline.f3/f2.vertline.<1.4
• 0.7<E1W/fW<1.5
• 0.83<E2W/fW<1.50
• where f2 and f3 are focal lengths of said second and third lens groups respectively, fW is a shortest focal length of the entire lens system, and E1W and E2W are intervals between principal points of said first and second lens groups and between principal points of said second and third lens groups in the wide-angle end respectively.

A zoom lens comprising, from front to rear, a first lens group of negative refractive power, a second lens group of positive refractive power and a third lens group of negative refractive power, and said third lens group includes at least two negative lenses lens in this order from the front, wherein as zooming from the wide-angle end to the telephoto end is performed by moving said first, second and third lens groups, said second and third lens groups are moved forward in such relation that said third lens group moves a longer distance than said second lens group, and the following conditions are satisfied:

• 0.14<f2/FT<0.28
• 1.5<S1w/S2w<4
• 0.2<.vertline.f3.vertline./FT<0.6
• 3<FT/FW<7
• where S1w and S2w are air separations between said first and second lens groups and between said second and third lens groups in the wide-angle end respectively, f2 and f3 are focal lengths of said second and third lens groups respectively, and FW and FT are shortest and longest focal lengths of the entire lens system respectively.

A zoom lens from front to rear, comprising:

• a first lens group of negative refractive power;
• a second lens group of positive refractive power;
• and
• third lens group comprising a positive lens and a negative lens in order from front to rear, said third lens group having an overall refractive power that is negative,
• wherein effective zooming is performed by varying spaces between said lens groups, and
• wherein focusing is performed by moving said third lens group, and
• wherein the zoom lens satisfies the following conditions:
• 1<f31/.vertline.f3.vertline.<2
• where f3 and f31 are focal lengths of said third lens group and said positive lens, respectively.