A camera system is disclosed, which can obtain an accurate target driving amount when the target driving amount of a focusing lens is calculated while the focusing lens is driven. The camera system has a camera and a lens apparatus which has an image taking optical system including a focusing lens and is mounted on the camera. The camera has a photoelectric conversion element which photoelectrically converts an optical image, a focus information producing section which produces focus information based on the output of the photoelectric conversion element, and a communication unit which transmits timing information of the photoelectric conversion and the focus information to the lens apparatus. The lens apparatus has a memory which stores an optical information changing according to the position of the focusing lens, and a controller which controls the driving of the focusing lens.