An optical system may include: a first lens having positive refractive power facing an object, the first lens having a first convex face facing the object; a second lens having positive refractive power, the second lens having a second convex face facing the object; a third lens having negative refractive power, the third lens having a third concave face facing an image sensor; a fourth lens adjacent to the third lens; a fifth lens adjacent to the fourth lens, the fifth lens having a fourth face facing the object, the fourth face being convex where the fifth lens intersects the optical axis; and a sixth lens adjacent to the fifth lens. The characteristics of the optical system satisfy equation, 0.4