A lens system, comprising: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens that are sequentially arranged in an optic axis direction from an object side to an image side, wherein the first lens has a positive refractive power, the second lens has a negative refractive power, the third lens has a negative refractive power, the fourth lens has a positive refractive power, and the fifth lens has a negative refractive power and has a convex image-side surface; wherein: the first lens has a convex object-side surface; the second lens has a convex image-side surface and has a concave object-side surface; the third lens has a concave image-side surface; and the fourth lens has a convex image-side surface; wherein: the first lens satisfies the following conditions: 0.3<f1/f<0.6, and -1.0<R1/R2<0, wherein f1 indicates the focal length of the first lens, R1 indicates a vertex curvature radius of the object-side surface of the first lens, and R2 indicates a vertex curvature radius of an image-side surface of the first lens; the second lens, the third lens, and the fifth lens have negative focal lengths, and satisfy the following conditions: - 0.8<f2/f<-0.1, and -100<R3/R4<100; - 0.8<f3/f<-0.1, and -100<R5/R6<100; and - 0.8<f5/f<-0.1, and -0.1<R9/R10<10, wherein f2 indicates the focal length of the second lens, f3 indicates the focal length of the third lens, f5 indicates the focal length of the fifth lens, R3 indicates a vertex curvature radius of the object-side surface of the second lens, R4 indicates a vertex curvature radius of the image-side surface of the second lens, R5 indicates a vertex curvature radius of an object-side surface of the third lens, R6 indicates a vertex curvature radius of the image-side surface of the third lens, R9 indicates a vertex curvature radius of an object-side surface of the fifth lens, and R10 indicates a vertex curvature radius of the image-side surface of the fifth lens; and the fourth lens has a positive focal length, and satisfies the following conditions: 0.4<f4/f<2.0, and 0<R7/R8<20, wherein f4 indicates the focal length of the fourth lens, R7 indicates a vertex curvature radius of an object-side surface of the fourth lens, and R8 indicates a vertex curvature radius of the image-side surface of the fourth lens. a first lens, a second lens, a third lens, a fourth lens, and a fifth lens that are sequentially arranged in an optic axis direction from an object side to an image side, wherein the first lens has a positive refractive power, the second lens has a negative refractive power, the third lens has a negative refractive power, the fourth lens has a positive refractive power, and the fifth lens has a negative refractive power and has a convex image-side surface; wherein: the first lens has a convex object-side surface; the second lens has a convex image-side surface and has a concave object-side surface; the third lens has a concave image-side surface; and the fourth lens has a convex image-side surface; the first lens has a convex object-side surface; the second lens has a convex image-side surface and has a concave object-side surface; the third lens has a concave image-side surface; and the fourth lens has a convex image-side surface; wherein: the first lens satisfies the following conditions: 0.3<f1/f<0.6, and -1.0<R1/R2<0, wherein f1 indicates the focal length of the first lens, R1 indicates a vertex curvature radius of the object-side surface of the first lens, and R2 indicates a vertex curvature radius of an image-side surface of the first lens; the second lens, the third lens, and the fifth lens have negative focal lengths, and satisfy the following conditions: - 0.8<f2/f<-0.1, and -100<R3/R4<100; - 0.8<f3/f<-0.1, and -100<R5/R6<100; and - 0.8<f5/f<-0.1, and -0.1<R9/R10<10, wherein f2 indicates the focal length of the second lens, f3 indicates the focal length of the third lens, f5 indicates the focal length of the fifth lens, R3 indicates a vertex curvature radius of the object-side surface of the second lens, R4 indicates a vertex curvature radius of the image-side surface of the second lens, R5 indicates a vertex curvature radius of an object-side surface of the third lens, R6 indicates a vertex curvature radius of the image-side surface of the third lens, R9 indicates a vertex curvature radius of an object-side surface of the fifth lens, and R10 indicates a vertex curvature radius of the image-side surface of the fifth lens; and - 0.8<f2/f<-0.1, and -100<R3/R4<100; - 0.8<f3/f<-0.1, and -100<R5/R6<100; and - 0.8<f5/f<-0.1, and -0.1<R9/R10<10, wherein f2 indicates the focal length of the second lens, f3 indicates the focal length of the third lens, f5 indicates the focal length of the fifth lens, R3 indicates a vertex curvature radius of the object-side surface of the second lens, R4 indicates a vertex curvature radius of the image-side surface of the second lens, R5 indicates a vertex curvature radius of an object-side surface of the third lens, R6 indicates a vertex curvature radius of the image-side surface of the third lens, R9 indicates a vertex curvature radius of an object-side surface of the fifth lens, and R10 indicates a vertex curvature radius of the image-side surface of the fifth lens; and the fourth lens has a positive focal length, and satisfies the following conditions: 0.4<f4/f<2.0, and 0<R7/R8<20, wherein f4 indicates the focal length of the fourth lens, R7 indicates a vertex curvature radius of an object-side surface of the fourth lens, and R8 indicates a vertex curvature radius of the image-side surface of the fourth lens.