A camera system includes a camera body including a photometering device and an external operating device, and a photographing lens which is detachably attached to the camera body, the photographing lens including an aperture setting device for selecting an auto aperture setting and at least one fixed aperture setting. A full-aperture photometering operation is performed when the aperture setting device is positioned at the auto aperture setting, and a stop-down photometering operation is performed in response to an operation of the external operating device when the aperture setting device is positioned at the fixed aperture setting.