| 摘要 |
An optical system including, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having negative refractive power. The second lens group has, in order from the object, a front group having negative refractive power and a rear group. In various embodiments, the following conditional expressions are satisfied, 0.4<f2F/f2<1.6 and−3.0<q2<−0.3 where f2 denotes a focal length of the second lens group, f2F denotes a focal length of the front group, and q2 denotes a form factor of a negative lens disposed closest to the object of the front group.
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