High zoom-ratio zoom lens system

A high zoom-ratio zoom lens system of five lens groups comprises a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a negative fifth lens group, in this order from an object,

• wherein upon zooming from the short focal length extremity to the long focal length extremity, a distance between said positive first lens group and said negative second lens group increases, and a distance between said negative second lens group and said positive third lens group decreases;
• and
• wherein said high zoom-ratio zoom lens system satisfies the following conditions:
• 4.5<f1/fw<10.0
• 1.4<fBw/fw<2.0
• wherein
• f1 designates the focal length of said positive first lens group;
• fw designates the focal length of the entire zoom lens system at the short focal length extremity, and
• fBw designates the back focal distance at the short focal length extremity.

A high zoom-ratio zoom lens system comprises a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in this order from the object,

• wherein upon zooming from the short focal length extremity to the long focal length extremity, a distance between said positive first lens group and said negative second lens group increases, and a distance between said negative second lens group and said positive third lens group decreases;
• and
• wherein said high zoom-ratio zoom lens system satisfies the following conditions:
• 5.5<f1/|f2|<10.0(f2<0)
• 1.7<f3/f4<4.0
• 4.5<f1/fw<10.0
• 1.4<fBw/fw<2.0
• wherein
• f1 designates the focal length of said positive first lens group;
• f2 designates the focal length of said negative second lens group;
• f3 designates the focal length of said positive third lens group;
• f4 designates the focal length of the positive fourth lens group;
• and
• fw designates the focal length of the entire zoom lens system at the short focal length extremity, and
• fBw designates the back focal distance at the short focal length extremity.

A high zoom-ratio zoom lens system of five lens groups comprises a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a negative fifth lens group, in this order from an object,

• wherein focusing is performed by moving said negative fifth lens group in the optical axis direction;
• and
• wherein said high zoom-ratio zoom lens system satisfies the following conditions:
• 2.2<m5t<3.5
• 2.0<f5/f2<5.0
• wherein
• m5t designates the lateral magnification of said negative fifth lens group at the long focal length extremity;
• f5 designates the focal length of said negative fifth lens group;
• and
• f2 designates the focal length of said negative second lens group.