A camera system including a camera body, an interchangeable lens, and an accessory mounted between the camera body and the interchangeable lens, wherein the accessory has a signal processing unit configured to process a signal input into the accessory and a storage unit configured to store information to be used when performing the signal processing, the camera system further including a pseudo interchangeable lens which can be mounted on the accessory instead of the interchangeable lens and which is configured to supply power from the camera body to the accessory when mounted on the camera body via the accessory, and a control unit configured to, while the camera body, the accessory, and the pseudo interchangeable lens are connected, when the accessory receives within a predetermined duration predetermined information, enable communication between the camera body and the accessory even after the predetermined duration has elapsed, and rewrite the information stored in the storage unit.