Patent ID: 8553335

Claim:
A zoom lens comprising: a first lens group having a positive refractive power, and a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power arranged in order from an object side, the third lens group comprised of a first positive lens, a second positive lens, and a negative lens, and a third positive lens in order from the object side; and an aperture stop disposed between the second lens group and the third lens group, wherein: when zooming from a short focal end to a long focal end, the zoom lens is moved so that an interval between the first and second lens groups increases, an interval between the second and third lens groups decreases, an interval between the third and fourth lens groups increases, and the first and third lens groups are positioned to be closer to the object side at the long focal end than the short focal end; and at least two of the first to third positive lenses are made from a material having a partial dispersion ratio P g, F defined by P g, F =(n g −n F )/(n F −n C ) which satisfies the following three conditions: 1.54 <n d <1.7 62 <v d <80 0.008 <P g, F −(−0.001802 *v d +0.6483)<0.050 where n d is a refractive index relative to a d-line, v d is Abbe number and n g , n F , n C are refractive indexes relative to a g-line, a F-line, a C-line, respectively.