Abstract: The objective of the present invention is to provide a zoom lens system having an f-number of approximately 1.3 at the wide extremity, a half angle-of-view of 75 degrees, and a zoom ratio of approximately 3:1. The solution to this objective is to provide a zoom lens system including a first lens group, having a negative refractive power, a diaphragm, and a second lens group, having a positive refractive power, in that order from the object side; wherein the first lens group and the second lens group move in the optical axis direction so that the distance therebetween decreases upon zooming from the wide-angle extremity to the telephoto extremity.

Abstract: The objective of the present invention is to provide a zoom lens system having an f-number of approximately 1.3 at the wide extremity, a half angle-of-view of 75 degrees, and a zoom ratio of approximately 3:1.

Abstract: A telephoto lens system of a four-lens-group arrangement includes a negative first lens group, a positive or negative second lens group, a negative third lens group and a positive fourth lens group. The telephoto lens system of the four-lens-group arrangement is constituted by less than six lens elements in total. The positive or negative second lens group is constituted by a positive lens element and a negative lens element which are cemented to each other, in this order from the object. The positive lens element has a convex surface with a larger curvature facing toward the object. The positive or negative second lens group satisfies the following condition: 0.8<f2p/|f2n|<1.4.

Abstract: A telephoto lens system of a four-lens-group arrangement includes a negative first lens group, a positive or negative second lens group, a negative third lens group and a positive fourth lens group. The telephoto lens system of the four-lens-group arrangement is constituted by less than six lens elements in total. The positive or negative second lens group is constituted by a positive lens element and a negative lens element which are cemented to each other, in this order from the object. The positive lens element has a convex surface with a larger curvature facing toward the object. The positive or negative second lens group satisfies the following condition: 0.8<f2p/|f2n|<1.4??(1) wherein f2p designates the focal length of the positive lens element in the second lens group; and f2n designates the focal length of the negative lens element in the second lens group.

Abstract: A surveillance camera system includes a photographing lens system, and a camera body to which the photographing lens system is detachably attached. The camera body includes a color imaging device on which an image formed by the photographing lens system is formed. The correcting of aberrations is carried out in a photographing lens system so that the difference between (1) the in-focus position at which the maximum MTF characteristic in the visible light wavelength range of about 400 nm to 700 nm is obtained and (ii) the in-focus position at which the maximum MTF characteristic in the near-infrared light wavelength range of about 700 nm to 1000 nm is obtained is less than 10&mgr;m.