Image-capturing optical system, image-capturing optical apparatus and digital device

An image-capturing optical system comprising:

• a positive first lens group;
• and
• a positive second lens group,
• wherein the positive first lens group and the positive second lens group are arranged in order from an object side in the image-capturing optical system,
• the image-capturing optical system focuses on a close object by moving the second lens group as a whole along a light axis toward the object side,
• a lens closest to the object side in the second lens group has a convex surface facing the object side,
• a lens closest to an image side in the second lens group is a positive meniscus lens having a convex surface facing the image side,
• the image-capturing optical system satisfies following condition expressions (1) to (3)
• 2.2<1Gr—Fl/FL<3.8 (1)
• 0.9<2Gr—Fl/FL<1.5 (2), and
• 0.45<1Gr—R—nop/1Gr—Thi<0.85 (3)
• the FL indicates a focal length of the image-capturing optical system,
• the 1Gr_Fl indicates a focal length of the first lens group,
• the 2Gr_Fl indicates a focal length of the second lens group,
• the 1Gr_R_nop indicates a distance from a surface closest to the object side to a position of a back principal point in the first lens group, and
• the 1Gr_Thi indicates a whole length of the first lens group.