Optical system and photographing device having optical system

An optical system, comprising:

• a first lens group having a positive refractive power, a second lens group having a negative refractive power and a third lens group having a positive or negative refractive power, sequentially arranged from an object side to an image side;
• when focusing, the second lens group moves along an optical axis, and positions of the first lens group and the third lens group relative to an imaging plane in a direction of the optical axis are fixed;
• where a lateral magnification of the third lens group focusing at infinity is b3, a distance from a face closest to the object side of the entire optical system to the imaging plane is OAL, a focal length of the optical system focusing at infinity is f, and a maximum lateral magnification of the entire optical system is B, it is satisfied that:
• 0.8
• ≤
• b
• ⁢
• 3
• ,
• OAL
• /
• f
• ≤
• 2.
• ,
• and
• 0.5
• ≤
• ❘
• "\[LeftBracketingBar]"
• B
• ❘
• "\[RightBracketingBar]"
• ;
• and
• wherein the second lens group has:
• at least one lens having a positive refractive power;
• and
• at least one lens having a negative refractive power,
• in the second lens group, a lens having the strongest positive refractive power is located closer to the image side than a lens having the strongest negative refractive power.