In order to be able to reduce power consumption while making possible manual operation in any scene when the photographic situation demands its use, an image pickup apparatus has a ring member arranged concentrically with the optical axis of lenses, a detecting device for detecting the quantity of variation resulting from the rotation of the ring member, a control device for shifting/stopping a group of optical lenses in the direction of their optical axis on the basis of the result of detection by the detecting device, and a power supply control device for changing the state of power supply to the detecting device according to the mode of use. Power supply to the detecting device is prohibited when in the automatic focusing mode, and permitted in a focusing-locked state when in the photo shooting mode. It is also prohibited in the viewing mode.