Variable magnification optical system, optical apparatus, and method for producing variable magnification optical system

A method for manufacturing a variable magnification optical system which comprises, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power and a rear lens group having negative refractive power;

• the method comprising the following steps:
• constructing such that, upon varying a magnification, a distance between the first lens group and the second lens group is varied, a distance between the second lens group and the third lens group is varied, and a distance between the third lens group and the rear lens group is varied;
• constructing such that the third lens group or the rear lens group comprises a focusing lens group which is moved upon carrying out focusing;
• and
• constructing such that the following conditional expressions are satisfied:
• 2.00<f1/fw<8.000
• 0.400<BFw/fw<1.300
• 4.000<f1/f1Rw<9.000
• where f1 denotes a focal length of said first lens group, fw denotes a focal length of said variable optical system in a wide angle end state, BFw denotes a back focus of said variable magnification optical system in the wide angle end state, and f1Rw denotes a composite focal length of lens groups in the wide angle end state disposed on the side which is closer to the image plane than the first lens group.

A variable magnification optical system comprises, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a rear lens group having negative refractive power;

• upon varying a magnification, a distance between said first lens group and said second lens group being varied, a distance between said second lens group and said third lens group being varied, and a distance between said third lens group and said rear lens group being varied;
• said third lens group or said rear lens group comprising a focusing lens group which is moved upon carrying out focusing;
• and
• the following conditional expressions being satisfied:
• 2.00<f1/fw<8.000
• 0.400<BFw/fw<1.300
• 0.300<|fF|/ft<1.000
• where f1 denotes a focal length of said first lens group, fw denotes a focal length of said variable magnification optical system in a wide angle end state, BFw denotes a back focus of said variable magnification optical system in the wide angle end state, fF denotes a focal length of the focusing lens group, and ft denotes a focal length of the variable magnification optical system in a telephoto end state.