Variable power zoom lens

A variable power zoom lens that has the foremost or first lens group of positive refractivity, the second lens group of negative refractivity, the third lens group of positive refractivity, and the fourth lens group of positive refractivity disposed in sequence from a position closer to the object to photograph toward the image plane, and the zoom lens meets requirements as defined in conditional formulae as follows:

• −1.5<F1/F—Bt<−0.5
• where F1 is a focal length of the first lens group, and F_Bt is the focal length from the front surface of the foremost lens piece in the second lens group to the image plane at the telephoto end.

A variable power zoom lens that has the foremost or first lens group of positive refractivity, the second lens group of negative refractivity, the third lens group of positive refractivity, and the fourth lens group of positive refractivity disposed in sequence from a position closer to the object to photograph toward the image plane, and the zoom lens meets requirements as defined in conditional formulae as follows:

• −3.5<βt<−1.55
• where βt is a lateral magnification of an anti-shake lens group at the telephoto end.

A variable power zoom lens that has the foremost or first lens group of positive refractivity, the second lens group of negative refractivity, the third lens group of positive refractivity, and the fourth lens group of positive refractivity disposed in sequence from a position closer to the object to photograph toward the image plane, and at least one of the lens groups shows two deflection points throughout a single stroke of the lens group during shifting from the wide-angle end to the telephoto end to vary magnification power.