Zoom lens system and image pickup apparatus having the same

A zoom lens system comprising, in order from an object side to an image side:

• a first lens unit of positive optical power;
• a second lens unit of negative optical power;
• a third lens unit of positive optical power;
• and
• a fourth lens unit of positive optical power,
• wherein zooming is performed by moving each of the lens units,
• wherein the first lens unit moves during zooming so that position of the first lens unit, which corresponds to a telephoto end, is closer to the object side than position of the first lens unit, which corresponds to a wide-angle end and the third lens unit moves during zooming so that position of the third lens unit, which corresponds to a telephoto end, is closer to the object side than position of the third lens unit, which corresponds to a wide-angle end,
• wherein an amount X1 of movement of the first lens unit on an optical axis during zooming from the wide-angle end to the telephoto end meets the following condition:
• 0.2<X1/ft<0.5, and
• wherein a ratio β2z of an imaging magnification of the second lens unit corresponding to the telephoto end, to an imaging magnification of the second lens unit corresponding to the wide-angle end, a ratio β3z of an imaging magnification of the third lens unit corresponding to the telephoto end, to an imaging magnification of the third lens unit corresponding to the wide-angle end, a focal length f2 of the second lens unit, and a focal length ft of the zoom lens system corresponding to the telephoto end meet the following conditions:
• 0.7<β2z/β3z<1.3, and
• −0.3≦f2/ft≦−0.1.

A zoom lens system comprising, in order from an object side to an image side:

• a first lens unit of positive optical power;
• a second lens unit of negative optical power;
• a third lens unit of positive optical power;
• and
• a fourth lens unit of positive optical power,
• wherein zooming is performed by moving each of the lens units,
• wherein the first lens unit moves during zooming so that position of the first lens unit, which corresponds to a telephoto end, is closer to the object side than position of the first lens unit, which corresponds to a wide-angle end and the third lens unit moves during zooming so that position of the third lens unit, which corresponds to a telephoto end, is closer to the object side than position of the third lens unit, which corresponds to a wide-angle end,
• wherein a ratio β2z of an imaging magnification of the second lens unit corresponding to the telephoto end, to an imaging magnification of the second lens unit corresponding to the wide-angle end, a ratio β3z of an imaging magnification of the third lens unit corresponding to the telephoto end, to an imaging magnification of the third lens unit corresponding to the wide-angle end, a focal length f2 of the second lens unit, and a focal length ft of the zoom lens system corresponding to the telephoto end meet the following conditions:
• 0.7<β2z/β3z<1.3, and
• −0.3≦f2/ft≦−0.1, and
• wherein an amount X3 of movement of the third lens unit on an optical axis during zooming from the wide-angle end to the telephoto end meets the following condition:
• 0.2<X3/ft<0.5.

A zoom lens system comprising, in order from an object side to an image side:

• a first lens unit of positive optical power;
• a second lens unit of negative optical power;
• a third lens unit of positive optical power;
• and
• a fourth lens unit of positive optical power,
• wherein zooming is performed by moving each of the lens units,
• wherein the first lens unit moves during zooming so that position of the first lens unit, which corresponds to a telephoto end, is closer to the object side than position of the first lens unit, which corresponds to a wide-angle end and the third lens unit moves during zooming so that position of the third lens unit, which corresponds to a telephoto end, is closer to the object side than position of the third lens unit, which corresponds to a wide-angle end,
• wherein a ratio β2z of an imaging magnification of the second lens unit corresponding to the telephoto end, to an imaging magnification of the second lens unit corresponding to the wide-angle end, a ratio β3z of an imaging magnification of the third lens unit corresponding to the telephoto end, to an imaging magnification of the third lens unit corresponding to the wide-angle end, a focal length f2 of the second lens unit, and a focal length ft of the zoom lens system corresponding to the telephoto end meet the following conditions:
• 0.7<β2z/β3z<1.3, and
• −0.3≦f2/ft≦−0.1,
• wherein an amount X1 of movement of the first lens unit on an optical axis and an amount X2 of the second lens unit on the optical axis during zooming from the wide-angle end to the telephoto end meet the following condition:
• 2.0 <X1/X2<4.0.