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.