Imaging lens system

An imaging lens system comprising:

• a first lens having a negative refractive power;
• a second lens having a refractive power;
• a third lens having a refractive power;
• a fourth lens having a refractive power;
• a fifth lens having a refractive power;
• and
• a sixth lens having a refractive power, a convex object-side surface in a paraxial region thereof, and a concave image-side surface in a paraxial region thereof,
• wherein the first to sixth lenses are sequentially disposed in ascending numerical order along an optical axis of the imaging lens system from an object side of the imaging lens system toward an image plane of the imaging lens system,
• the imaging lens system has a total number of six lenses having a refractive power,
• one or more of the first to fifth lenses is configured to be movable in an optical axis direction of the imaging lens system,
• f-number<2.60, where f-number is an f-number of the imaging lens system,
• 3.0<(R12+R11)/(R12−R11)<7.0 is satisfied, where R11 is a radius of curvature of the object-side surface of the sixth lens at the optical axis, and R12 is a radius of curvature of the image-side surface of the sixth lens at the optical axis,
• the one or more of the first to fifth lenses is configured to be movable in the optical axis direction to vary a focal length of the imaging lens system, and
• 1.0<f6/fF<1.3 is satisfied, where fF is a maximum focal length of the imaging lens system, and f6 is a focal length of the sixth lens.