Lens system, interchangeable lens apparatus and camera system

A lens system comprising lens units each being composed of at least one lens element, including:

• a most-object-side lens unit located closest to an object side;
• a first most-image-side lens element located closest to an image side;
• and
• a second most-image-side lens element located immediately on the object side relative to the first most-image-side lens element, wherein
• the most-object-side lens unit has positive optical power and is fixed with respect to an image surface in focusing from an infinity in-focus condition to a close-object in-focus condition,
• at least one of the first most-image-side lens element and the second most-image-side lens element has negative optical power, and the following conditions (3)′ and (7) are satisfied:
• 0.5<DAIR/Y (3)′
• 1.5<DIM/DOB<4.0 (7)
• where
• DAIR is a maximum value of air spaces between the lens elements constituting the lens system in the infinity in-focus condition,
• Y is a maximum image height expressed by the following formula:
• Y=f×tan ω
• f is a focal length of the lens system,
• ω is a half view angle of the lens system,
• DOB is an optical axial thickness of the most-object-side lens unit, and
• DIM is an optical axial distance from an object side surface of a most-object-side lens element in a lens unit located immediately on the image side relative to the most-object-side lens unit, to an image side surface of the first most-image-side lens element.