A lens unit has a photographing lens, and is secured removably to a camera main body. An accessory conversion lens device is settable on the lens unit. The lens unit includes a reception unit for receiving accessory device data from the conversion lens device. A determiner checks propriety of the conversion lens device according to accessory device data received by the reception unit, and produces checking information. A transmission unit transmits the checking information to the main body. Specifically, the lens unit has an image pickup element. Also, the conversion lens device includes an RFID tag for storing the accessory device data. The reception unit includes an RFID tag reader for wireless reception. Also, the main body includes an LCD panel to display for outputting alarm information. A main body controller drives the LCD panel if the checking information represents lack of the propriety.