Accessory apparatus, camera system having the same, and storage medium

A camera system comprising:

• an accessory apparatus;
• and
• a camera including an image sensor configured to photoelectrically convert an object image and to output an electric signal, wherein the accessory apparatus is detachably attached to the camera,
• wherein the accessory apparatus includes an accessory controller configured to control a communication with the camera using a notification channel used to transmit a signal between the camera and the accessory apparatus and a data communication channel used for a data communication between the camera and the accessory apparatus,
• wherein the accessory controller is configured to switch between a first communication method used for communications between the camera and all accessory apparatuses connected to the camera and a second communication method used for an individual communication with the camera, and
• wherein the accessory controller is configured to switch, in the second communication method, from the second communication method to the first communication method when detecting a start of the data communication in the first communication method in the communication.