Zoom lens system having a high zoom ratio

A zoom lens system, comprising:

• a first lens group having a positive power;
• a second lens group having a negative power and a magnification varying function, said second lens group being movable during a zooming operation;
• a third lens group having a negative power and a focus compensating function, said third lens group being movable during said zooming operation;
• and,
• a fourth lens group having a positive power and an image forming function, said fourth lens group not being movable during said zooming operation,
• wherein said first, second, third, and fourth lens groups are arranged in this order from an object side,
• said fourth lens group being comprised of a first sub-lens group and a second sub-lens group each having a positive power, in this order from said object side, said first sub-lens group and said second sub-lens group having a predetermined distance therebetween,
• and further wherein said zoom lens system satisfies the following relationships:
• 0.25<L.sub.W2-3 /f.sub.T <0.4
• 0.2<.vertline.m.sub.2W .vertline.<0.4 (m.sub.2W <0)
• 1.0<.vertline.m.sub.4 .vertline.<1.4 (m.sub.4 <0)
• 0.5<m.sub.4b <0.9
• 1.3<f.sub.4 /f.sub.4a <2.5
• wherein
• L.sub.W2-3 represents a distance between said second lens group and said third lens group at a shortest focal length extremity,
• f.sub.T represents a focal length of the whole lens system at a longest focal length extremity,
• m.sub.2W represents a lateral magnification of said second lens group at said shortest focal length extremity,
• m.sub.4 represents a lateral magnification of said fourth lens group,
• m.sub.4b represents a lateral magnification of said second sub-lens group of said fourth lens group,
• f.sub.4 represent a focal length of said fourth lens group, and
• f.sub.4a represents a focal length of said first sub-lens group of said fourth lens group.