Patent ID: 8498063

Claim:
A telephoto lens system comprising: a first lens group having a positive refractive power and comprising at least three positive lenses and one negative lens; a second lens group having a negative refractive power and performs focusing by moving along the optical axis; and a third lens group having a positive refractive power and comprising a 3a sub-lens group with positive refractive power and a 3b sub-lens group, wherein: the 3a sub-lens group comprises a negative lens and a positive lens sequentially arranged from an object side, the 3b sub-lens group comprises a positive lens and a negative lens sequentially arranged from the object side, and the telephoto lens system satisfies the condition, 0.17<fb/f <0.35, where, fb indicates the back focal length in air without a filter, that is, the distance from the lens surface of the telephoto lens system closest to the image side to the imaging surface with respect to the telephoto lens system having an optical arrangement at an infinite object position in air without the filter, and f indicates the overall focal length of the telephoto lens system.