Photographing lens

1. A photographing lens comprising, in order from an object side:

a first lens having a positive refractive power and a convex surface facing the object side;

a second lens having a negative refractive power;

a third lens having a positive refractive power; and

a fourth lens having a negative refractive power and at least one aspheric surface,

the photographing lens satisfying the following conditional expressions:

L

T

f

≤

1.2

0.5

≤

f

3

f

≤

1.0

wherein L T denotes the distance on the optical axis between the object side of the first lens and the image side of the fourth lens; f denotes the total focal length of the photographing lens; and f 3 denotes the focal length of the third lens.

2. The photographing lens as claimed in claim 1 , wherein the third lens has at least one aspheric surface.

3. The photographing lens as claimed in claim 1 , wherein the photographing lens further satisfies the following conditional expressions:

0.5

≤

f

1

f

≤

2.0

⁢

-

1.2

≤

f

2

f

≤

-

0.4

wherein f 1 denotes the focal length of the first lens; and f 2 denotes the focal length of the second lens.

4. The photographing lens as claimed in claim 1 , wherein the photographing lens further satisfies the following conditional expressions:

| n 3 −n 4 |≧0.1

wherein n 3 denotes the refractive index of the third lens; and n 4 denotes the refractive index of the fourth lens.

5. The photographing lens as claimed in claim 1 , wherein the photographing lens further satisfies the following conditional expressions:

-

20

≤

f

4

f

≤

-

1

wherein f 4 denotes the focal length of the fourth lens.