Patent ID: 8780451

Claim:
A zoom lens system, in order from an object side to an image side, comprising a first lens unit having negative optical power, a second lens unit having positive optical power, a third lens unit having negative optical power, and a fourth lens unit having positive optical power, wherein the second lens unit is, in order from the object side to the image side, composed of an object-side second lens unit and an image-side second lens unit, the object-side second lens unit has positive optical power, an aperture diaphragm is located between the object-side second lens unit and the image-side second lens unit, and the following conditions (1) and (2) are satisfied: −0.5 <f 2O /f 2I <1.0 (1) 0.12 <d 2O /f W <0.35 (2) where f 2O is a composite focal length of the object-side second lens unit, f 2I is a composite focal length of the image-side second lens unit, d 2O is an optical axial distance from a most object side lens surface of the object-side second lens unit to the aperture diaphragm, and f W is a focal length of the entire system at a wide-angle limit.