Projection lens system with magnification-varying capability and projector

A projection lens system that performs a zoom by varying distances between a plurality of lens groups, the projection lens system comprising:

• a first lens group comprising:
• a 1a-th lens group having a negative refractive power,
• a 1b-th lens group having a positive or negative refractive power, and
• a 1c-th lens group having a positive or negative refractive power,
• wherein, during a zoom, the first lens group remains stationary on an optical axis,
• wherein, during a focus from a remote distance side to a close distance side, the 1a-th lens group remains stationary on the optical axis while the 1b-th and 1c-th lens groups move toward the enlargement conjugate side along different loci respectively, and
• wherein conditional formula (1) below is fulfilled at both the remote and close distance sides:
• −4.7<fl/fw<−2.5 (1)
• where
• fl represents a focal length of the first lens group;
• and
• fw represents a focal length of the entire system at a wide-angle end.