Patent ID: 7339745

Claim:
A zoom lens system comprising, in order from an object side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a negative refractive power, wherein a space between the first lens unit and the second lens unit changes during magnification change, a space between the second lens unit and the third lens unit changes during the magnification change or a focusing operation; at least the second lens unit and the third lens unit move to the only object side during the magnification change from a wide-angle end to a telephoto end so that the space between the first lens unit and the second lens unit is narrower in the telephoto end than in the wide-angle end; the first lens unit comprises, in order from the object side, two lenses including a negative lens and a positive lens, the total number of the lenses included in the first lens unit is two; the second lens unit comprises at most three lenses; the third lens unit comprises a negative lens, the total number of the lenses included in the third lens unit is one; and the following conditions (1) and (2) are satisfied: 0.7 <C j ( t )/ C j ( w )<1.2 (1); and 1.6<β 2 ( t )/β 2 ( w )<2.5 (2), in which C j (w) is a distance from an incidence surface of the first lens unit to an image surface of the zoom lens system in the wide-angle end, C j (t) is a distance from the incidence surface of the first lens unit to the image surface of the zoom lens system in the telephoto end, β 2 (w) is a lateral magnification of the second lens unit in the wide-angle end, and β 2 (t) is a lateral magnification of the second lens unit in the telephoto end.