Zoom lens system

A zoom lens system comprising a positive first lens group and a negative second lens group, in this order from an object,

• wherein zooming is performed by moving each of said positive first lens group and said negative second lens group in an optical axis direction;
• wherein said positive first lens group comprises a positive first lens element having a convex surface facing toward said object, a negative second lens element, and a positive third lens element, in this order from said object;
• wherein said negative second lens group comprises a fourth lens element which is formed as a positive meniscus lens element having the concave surface facing toward said object, and a fifth lens element which is formed as a negative meniscus lens element having the concave surface facing toward said object, in this order from said object;
• and
• wherein said zoom lens system satisfies following conditions:
• 1.2<ft/f1<1.8
• 3.8<ft/f1G<4.2
• 1<SF1<6
• 0.45<ΔX/ft<0.50
• wherein
• ft designates the focal length of the entire zoom lens system at the long focal length extremity;
• f1 designates the focal length of said positive first lens element;
• f1G designates the focal length of said positive first lens group, and
• SF1 designates the shape factor of said positive first lens element, defined as SF1=(r2+r1)/(r2−r1);
• r1 designates the radius of curvature of the first surface of said positive first lens element;
• r2 designates the radius of curvature of the second surface of said positive first lens element;
• and
• ΔX designates the traveling distance of said positive first lens group upon zooming from the short focal length extremity to the long focal length extremity.