High zoom ratio zoom lens

A high zoom ratio lens comprising in order from an object side:

• a first lens unit having positive refractive power;
• a second lens unit having negative refractive power;
• a third lens unit having positive refractive power;
• and
• a fourth lens unit having positive refractive power, wherein during zooming from a maximum wide-angle state to a maximum telephoto state, said first, second, third and fourth lens units are caused to move toward the object such that the distance between said first lens unit and said second lens unit increases, the distance between said second lens unit and said third lens unit decreases, and the distance between said third lens unit and said fourth lens unit decreases, and wherein the following conditions are satisfied:
• 0. 05<.vertline.f2.vertline./ft<0.10 (f2<0)
• Z34>2
• mv1/fw>1.5
• 0.2<mv2/mv1<0.5
• where
• f2=focal length of said second lens unit,
• ft=focal length of the entire zoom lens at the maximum telephoto state,
• fw=focal length of the entire zoom lens at the maximum wide-angle state,
• Z34=ratio of the combined imaging magnification of said third lens unit and said fourth lens unit at the maximum telephoto state to the combined imaging magnification of said third lens unit and said fourth lens unit at the maximum wide-angle state,
• mv1=displacement of said first lens unit during zooming from the maximum wide-angle state to the maximum telephoto state, and
• mv2=displacement of said second lens unit during zooming from the maximum wide-angle state to the maximum telephoto state;
• and
• wherein the zoom lens includes a focal length shorter than a length of a diagonal of an effective picture plane of the zoom lens and a focal length longer than three times the length of the diagonal of the effective picture plane.

A high zoom ratio zoom lens comprising in order from an object side:

• a first lens unit having positive refractive power;
• a second lens unit having negative refractive power;
• a third lens unit having positive refractive power;
• and
• a fourth lens unit having positive refractive power, wherein during zooming from a maximum wide-angle state to a maximum telephoto state, said first, second, third and fourth lens units move toward the object such that the distance between said first lens unit and said second lens unit increases, the distance between said second lens unit and said third lens unit decreases, and the distance between said third lens unit and said fourth lens unit decreases, and wherein the following conditions are satisfied:
• 0.15<K(f)<0.45 for fw<f<2fw
• 0.25<K(f)<0.5 for 2fw<f<3fw
• 0.3<K(f)<0.45 for 3fw<f<4fw
• 0.25<K(f)<0.4 for 4fw<f<5fw
• 0.2<K(f)<0.4 for 5fw<f
• 0.05<.vertline.f2.vertline./ft<0.10 (f2<0)
• Z34>2
• mv1/fw>1.5
• 0.2<mv2/mv1<0.5
• where
• fw=focal length of the entire zoom lens at the maximum wide-angle state,
• f=focal length of the entire zoom lens at any focal length state between the maximum wide-angle state and the maximum telephoto state,
• K(f)=ratio of zooming displacements of said first lens unit and said second lens unit respectively from the maximum wide-angle state to the focal length state having the focal length f for the entire zoom lens,
• f2=focal length of said second lens unit,
• ft=focal length of the entire zoom lens at the maximum telephoto state,
• Z34=ratio of the combined imaging magnification of said third lens unit and said fourth lens unit at the maximum telephoto state to the combined imaging magnification of said third lens unit and said fourth lens unit at a maximum wide-angle state,
• mv1=displacement of said first lens unit during zooming from the maximum wide-angle state to the maximum telephoto state, and
• mv2=displacement of said second lens unit during zooming from the maximum wide-angle state to the maximum telephoto state;
• and
• wherein the zoom lens includes a focal length shorter than a length of a diagonal of an effective picture plane of the zoom lens and a focal length longer than three times the length of the diagonal of the effective picture plane.