Zoom lens system, imaging device and camera

A zoom lens system having a plurality of lens units, the zoom lens system, in order from an object side to an image side, comprising:

• a first lens unit having, as a unit, positive optical power, the first lens unit being constituted by either one or two lens elements;
• a second lens unit having, as a unit, negative optical power, the second lens unit being composed of at least one lens element;
• a third lens unit having, as a unit, positive optical power, the third lens unit being constituted by four or more lens elements, with an adjacent two of the third-lens-unit constituting lens elements each having negative optical power;
• a fourth lens unit, composed of at least one lens element;
• at least one subsequent lens unit;
• and
• a light-quantity adjusting aperture diaphragm;
• wherein
• the at least one subsequent lens unit includes a lens unit having negative optical power,
• the aperture diaphragm is located between the adjacent two of the lens elements constituting the third lens unit and each having negative optical power,
• in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit and the second lens unit move along an optical axis, and
• the following conditions (1), (2), and (3) are satisfied:
• 0.0<LGmax/LG2<1.5 (1)
• 0.5<|f2/fW|<20 (2)
• 0.3<|fe/f2|<70 (3)
• where,
• LGmax is a maximum value of an optical axial thickness of the at least one subsequent lens unit,
• LG2 is an optical axial thickness of the second lens unit,
• fW is a focal length of the zoom lens system at a wide-angle limit,
• f2 is a focal length of the second lens unit, and
• fe is a focal length of a lens unit having negative optical power and located closest to the image side in the zoom lens system.