Patent ID: 8432618

Claim:
A zoom lens system, in order from an object side to an image side, consisting of a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, wherein the third lens unit is composed of three or more lens elements, and wherein the following conditions are satisfied: nd 8 ≦1.5 and vd 8 ≧75, ( nd 9 −1)+( nd 10 −1)≧1.55, 16 <f T /f W , and ω>35, where nd 8 is a refractive index to the d-line of a lens element arranged on the most object side in the third lens unit, nd 9 is a refractive index to the d-line of a lens element arranged at the second position from the object side in the third lens unit, nd 10 is a refractive index to the d-line of a lens element arranged at the third position from the object side in the third lens unit, vd 8 is an Abbe number to the d-line of a lens element arranged on the most object side in the third lens unit, ω is a half view angle (°) at a wide-angle limit, f T is a focal length of the entire system at a telephoto limit, and f W is a focal length of the entire system at a wide-angle limit.