Patent ID: 8169533

Claim:
A zoom lens system comprising, in order from an object side to an image side: a first lens unit which does not move for zooming and has a positive refractive power; a second lens unit which moves toward the image side during zooming from a wide angle end to a telephoto end and has a negative refractive power; a third lens unit which moves during zooming; and a fourth lens unit which does not move for zooming, wherein the fourth lens unit includes, in order from the object side to the image side, a front subunit and a rear subunit, wherein the front subunit and the rear subunit are opposed to each other with an air interval sandwiched therebetween, the air interval being maximum among air intervals in the fourth lens unit, wherein the rear subunit includes two negative lenses and at least three positive lenses, wherein the rear subunit includes a first rear-subunit and a second rear-subunit, wherein a center position in a thickness direction of at least one lens included in the first rear-subunit is located in the object side of a center position of a total-length of the rear subunit in the optical axis direction, and a center position in a thickness direction of at least one lens included in the second rear-subunit is located in the image side of the center position of the total-length of the rear subunit in the optical axis direction, wherein each of the first rear-subunit and the second rear-subunit includes a negative lens and a positive lens, wherein the following conditions are satisfied: 0.50<ν1 p/ν 1 n< 1.10; and 2.30<ν2 p/ν 2 n, where ν1p and ν2p indicate an average Abbe number of materials of the positive lens of the first rear-subunit and an average Abbe number of materials of the positive lens of the second rear-subunit, respectively, and ν1n and ν2n indicate an Abbe number of a material of the negative lens of the first rear-subunit and an Abbe number of a material of the negative lens of the second rear-subunit, respectively, wherein an angle of field of the zoom lens system at the wide angle end is equal to or greater than 78 degrees, and wherein the first lens unit includes in order from the most-object side: a first meniscus lens having a negative refractive power with a convex surface facing the object side; a second meniscus lens having a negative refractive power with a convex surface facing the object side; a third negative lens; a fourth positive lens; and a fifth positive lens.