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

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

• upon varying a magnification, respective distances between neighboring lens groups being varied;
• the first lens group comprising a negative lens at a most object side and a positive lens at a most image side;
• the second lens group comprising, in order from the object side, a 2a lens group having positive refractive power, a 2b lens group having positive refractive power and a 2c lens group;
• the 2b lens group comprising a negative lens;
• and
• the following conditional expressions being satisfied:
• 0.05
• <
• f
• ⁢
• 21
• /
• f
• ⁢
• 22
• <
• 3.
• -
• 16.
• <
• (
• -
• f
• ⁢
• 23
• )
• /
• ft
• <
• 5.
• 1.1
• <
• f
• ⁢
• 12
• /
• (
• -
• f
• ⁢
• 1
• )
• <
• 4.
• 0.5
• <
• (
• -
• f
• ⁢
• 3
• )
• /
• fw
• <
• 2.5
• 50.
• °
• <
• 2
• ⁢
• ω
• <
• 120.
• °
• 0.2
• <
• Bfa
• /
• fw
• <
• 0.9
• where f21 denotes a focal length of the 2a lens group, f22 denotes a focal length of the 2b lens group, f23 denotes a focal length of the 2c lens group, ft denotes a focal length of the variable magnification optical system as a whole in a telephoto end state, f12 denotes a focal length of the positive lens, f1 denotes a focal length of the first lens group, f3 denotes a focal length of the third lens group, fw denotes a focal length of the variable magnification optical system in as a whole a wide angle end state, 2ω denotes an entire angle of view of the variable magnification optical system in the wide angle end state, and Bfa denotes an air converted back focus of the variable magnification optical system as a whole in the wide angle end state.