OPTICAL SYSTEM AND OPTICAL APPARATUS

原文（中国語）

An optical system includes an aperture stop that has a variable opening diameter and that determines an F number of the optical system, in which at least one positive lens and at least one negative lens are disposed closer to an object side than the aperture stop, and at least one positive lens and at least one negative lens are disposed closer to an image side than the aperture stop. An image side surface of at least one negative lens among the negative lenses disposed closer to the object side than the aperture stop has a concave shape. The optical system satisfies a predetermined conditional expression.