A camera system includes: a lens assembly and a camera body. The lens assembly has: an image-taking optical system, a storage section that stores screen information for display on an input screen, a screen transmission section that transmits the screen information, an information receiving section that receives the information entered according to the input screen, and a function execution section that executes a function according to the information received by the information receiving section. The camera body has: a connection section on which the lens assembly is detachably mounted, an image processing section that processes image data of the subject light image formed through the image-taking optical system, a screen receiving section that receives the screen information, a display input section that displays the input screen and receives information input according to the input screen, and an information transmitting section that transmits information entered through the display input section.