Patent ID: 6970298

Claim:
A zoom lens system comprising: lens units consisting of, in order from an object side to an image side: a first lens unit of negative optical power, the first lens unit consisting of, in order from the object side to the image side, a first lens element of negative optical power having an aspheric surface, a second lens element of negative optical power having a meniscus shape with a convex surface facing the object side, and a third lens element of positive optical power; a second lens unit of positive optical power, the second lens unit consisting of, in order from the object side to the image side, a fourth lens element of positive optical power, a fifth lens element of positive optical power, and a sixth lens element of negative optical power; a third lens unit of positive optical power, the third lens unit consisting of a seventh lens element of positive optical power; and a fourth lens unit of positive optical power, the fourth lens unit consisting of an eighth lens element of positive optical power, spaces between the first and second lens units, between the second and third lens units, and between the third and fourth lens units, wherein, during zooming from a wide-angle end to a telephoto end, the space between the first lens unit and the second lens unit decreases, the space between the second lens unit and the third lens unit varies, and the space between the third lens unit and the fourth lens unit increases, and wherein a refractive index of material of the first lens element (n 11 ), a refractive index of material of the second lens element (n 12 ), a focal length of the first lens element (f 11 ), and a focal length of the second lens element (f 12 ) satisfy the following conditions: 1.85<( n 11 + n 12 )/2<1.95 1.5 <f 11 / f 12 <2.5.