Abstract: An interchangeable lens assembly includes a plurality of lens-side claw portions and a lock pin concave portion. Furthermore, internal angles of a quadrangle formed by connecting a center of a first lens-side claw portion, a center of a second lens-side claw portion, a center of a third lens-side claw portion, and a center of the lock pin concave portion satisfies a predetermined condition.

Abstract: An interchangeable lens assembly includes a plurality of lens-side claw portions configured to enable engagement with a plurality of camera-side claw portions, and a lock pin concave portion in which a lock pin is inserted. Furthermore, ?1 is an angle formed by a line passing through a fifth lens-side end and an optical axis, and a line passing through a center of a lock pin concave portion and the optical axis, and ?2 is an angle formed by a line passing through a fourth lens-side end and the optical axis, and a line that passes through the center of the lock pin concave portion and the optical axis. In the above, ?1 and ?2 satisfy a predetermined conditional expression.

Abstract: An adapter device includes a first mount on one side and a second mount on another side. The first mount is detachably mounted to an imaging apparatus, and the second mount is detachably mounted to an accessory. The first mount has first through third mount recesses and first through third mount claws, disposed following a circumferential direction. The second mount has fourth through sixth mount recesses and fourth through sixth mount claws, disposed following the circumferential direction. The first through third mount claws are insertable to mount recesses on another imaging apparatus. The fourth through sixth mount claws are insertable to mount recesses on another accessory. A smallest angle range out of angle ranges in the circumferential direction of the first through third mount recesses is equal to or smaller than a smallest angle range out of angle ranges in the circumferential direction of the fourth through sixth mount claws.

Abstract: An accessory configured to be detachably mountable to an image pickup apparatus including a first mount portion including first bayonet claw portions, and first terminals, the accessory including a second mount portion including second bayonet claw portions configured to enable engagement with the first bayonet claw portions, and second terminals configured to enable contact with the first terminals, in which the second terminals are provided at positions that are different from positions of the second bayonet claw portions, and wherein, a half line that extends from a central axis of the second mount portion and passes through a second terminal that determines whether an optical apparatus is mounted on the image pickup apparatus or not, passes through a predetermined second bayonet claw portion.