Accessory, image pickup apparatus on which same is mountable, and camera system

A lens mount configured to be detachably mountable to a camera mount that includes a restricting portion and a plurality of first bayonet claw portions, the lens mount comprising:

• a plurality of second bayonet claw portions configured to allow engagement with the plurality of first bayonet claw portions;
• and
• a restricted portion configured to be restricted by the restricting portion when the lens mount is mounted to the camera mount,
• wherein, the plurality of second bayonet claw portions includes first and second claw portions adjacent to the restricted portion in a circumferential direction,
• wherein the plurality of first bayonet claw portions includes third and fourth claw portions adjacent to the restricting portion in the circumferential direction, and fifth claw portion disposed on opposite side of the restricting portion with respect to the third and fourth claw portions in the circumferential direction,
• wherein, when the lens mount is mounted to the camera mount, the first claw portion engages with the third claw portion after being inserted between the third and fifth claw portions in the circumferential direction, and the second claw portion engages with the fourth claw portion after being inserted between the third and fourth claw portions in the circumferential direction,
• wherein, when viewed in a central axis direction of the lens mount, a first reference line is a line passing through a center of the restricted portion and a central axis of the lens mount, a first line is a line passing through the central axis and an end of the first claw portion that is closer to the restricted portion, and a second line is a line passing through the central axis and an end of the second claw portion that is closer to the restricted portion,
• wherein the restricted portion is positioned at a region between the first line and the second line, and
• wherein
• 90°<θ1+θ2<180°
• is satisfied, where θ1 is an angle formed between the first reference line and the first line, and θ2 is an angle formed between the first reference line and the second line.