Patent ID: 7535654

Claim:
A zoom lens for photographing an image of an object, comprising: at least a first lens group having a positive refracting power; at least a second lens group placed on an image side of the first lens group having a negative refracting power; and at least a third lens group placed on an image side of the second lens group having a positive refracting power, the third lens group having at least a positive lens, when changing magnification from a wide-angle end toward a telephoto end, a spacing between the first lens group and the second lens group increasing, and a spacing between the second lens group and the third lens group decreasing, on an orthogonal two-dimensional coordinate plane taking a partial dispersion ratio θ g,F defined by the formula: θ g,F =(n g −n F )/(n F −n c ), whereat n g is a refractive i to a g line, n F is a refractive index to an F line, and n c is a refractive index to a c line, on the vertical axis, and taking an Abbe number ν d on the horizontal axis, when a straight line connecting a coordinate point (ν d =60.49, θ g,F =0.5432) of a standard glass type K7 and a coordinate point (ν d =36.26, θ g,F =0.5830) of a standard glass type F2 being defined as a standard line, and a deviation of the partial dispersion ratio θ g,F of the glass type from the standard line on the two-dimensional coordinate plane being defined as an anomalous dispersiveness Δθ g,F of the glass type, a refractive index N d and the Abbe number ν d and the anomalous dispersiveness Δθ g,F of the positive lens of the third lens group satisfying the following condition (1) through the condition (3) N d >1.58 (1) ν d >60.0 (2) 0.05>Δθ g,F >0.003. (3)