Magnification-variable optical system, optical apparatus, and method for manufacturing magnification-variable optical system

A method for manufacturing a magnification-variable optical system including a first lens group and a rear group, the first lens group having negative refractive power, the rear group including at least one lens group disposed on an image side of the first lens group, the method for manufacturing the magnification-variable optical system comprising:

• disposing the lens groups so that a distance between lens groups adjacent to each other changes at magnification change;
• and
• disposing the first lens group so that the first lens group consists of, sequentially from the object side, a negative single lens, a negative single lens, a negative single lens, and a positive single lens;
• the method further comprising:
• satisfying the following conditional expressions:
• −4.00<(L1r2+L1r1)/(L1r2−L1r1)<−0.50
• 100.00°<2ωw
• 1.42<(−f1)/fw<2.00
• 1.314≤fL1/f1<2.00
• 0.058≤(L3r2+L3r1)/(L3r2−L3r1)<0.80
• where
• L1r1:
• radius of curvature of a lens surface of a lens closest to an object side in the first lens group, the lens surface being on the object side,
• L1r2:
• radius of curvature of a lens surface of the lens closest to the object side in the first lens group, the lens surface being on an image side,
• 2ωw:
• full angle of view of the magnification-variable optical system in a wide-angle state,
• fw:
• focal length of the magnification-variable optical system in the wide-angle state,
• f1:
• focal length of the first lens group,
• fL1:
• focal length of the lens closest to the object side in the first lens group,
• L3r1:
• radius of curvature of a lens surface of a lens third closest to the object side in the first lens group, the lens surface being on the object side, and
• L3r2:
• radius of curvature of a lens surface of the lens third closest to the object side in the first lens group, the lens surface being on the image side.

A magnification-variable optical system comprising:

• a first lens group having negative refractive power;
• and
• a rear group including at least one lens group disposed on an image side of the first lens group, wherein
• a distance between lens groups adjacent to each other changes at magnification change,
• the first lens group consists of, sequentially from the object side, a negative single lens, a negative single lens, a negative single lens, and a positive single lens, and
• the following conditional expressions are satisfied:
• −4.00<(L1r2+L1r1)/(L1r2−L1r1)<−0.50
• 100.00°<2ωw
• 1.42<(−f1)/fw<2.00
• 1.314≤fL1/f1<2.00
• where
• L1r1:
• radius of curvature of a lens surface of a lens closest to an object side in the first lens group, the lens surface being on the object side,
• L1r2:
• radius of curvature of a lens surface of the lens closest to the object side in the first lens group, the lens surface being on an image side,
• 2ωw:
• full angle of view of the magnification-variable optical system in a wide-angle state,
• fw:
• focal length of the magnification-variable optical system in the wide-angle state,
• f1:
• focal length of the first lens group, and
• fL1:
• focal length of the lens closest to the object side in the first lens group.