Optical system and image pickup apparatus

An image pickup apparatus comprising:

• an optical system;
• and
• an image sensor configured to capture an image of an object through the optical system,
• wherein the optical system includes:
• a front lens unit;
• a first focus lens unit disposed on an image side of the front lens unit;
• and
• a second focus lens unit disposed on the image side of the first focus lens unit,
• wherein a distance between adjacent lens units changes during focusing,
• wherein the front lens unit includes two or more negative lenses,
• wherein for focusing, the front lens unit does not move, but the first focus lens unit and the second focus lens unit move,
• wherein the optical system can provide focusing from an in-focus state on an object at infinity to an in-focus state in which lateral magnification β of the optical system is −1.0 or less, and
• wherein the following inequality is satisfied:
• -
• 5
• .
• 5
• ⁢
• 00
• ≤
• ❘
• "\[LeftBracketingBar]"
• ffr
• ❘
• "\[RightBracketingBar]"
• /
• f
• ⁢
• 1
• ≤
• 0
• .
• 3
• ⁢
• 8
• ⁢
• 0
• where f1 is a focal length of the front lens unit, and ffr is a focal length of at least one of the first focus lens unit and the second focus lens unit.