Patent ID: 8049969

Claim:
A zoom lens system comprising, in order from an object side to an image side: a first lens unit having a negative refracting power; a second lens unit having a positive refracting power; a third lens unit having a negative refracting power; and a fourth lens unit having a positive refracting power, wherein at the time of zooming from a wide angle end to a telephoto end, distances between the lens units change by at least the first lens unit, the second lens unit, and the third lens unit being moved; and the second lens unit comprises in order from the object side, a first sub-unit having a positive refracting power, a second sub-unit having a negative refracting power, and a third sub-unit having a positive refracting power, and a surface on the object side and a surface on the image side of each of the first sub-unit, the second sub-unit, and the third sub-unit are in contact with air, and the second lens unit does not include other sub-units, and satisfies the following conditional expression (1) 3.2<(β 2t /β 2w )/(β 3t /β 3w )<7 (1) where, β 2t denotes a lateral magnification at the telephoto end of the second lens unit, β 2w denotes a lateral magnification at the wide angle end of the second lens unit, β 3t denotes a lateral magnification at the telephoto end of the third lens unit, and β 3w denotes a lateral magnification at the wide angle end of the third lens unit.