The present invention provides a lens barrel apparatus dispensing with deliberate switching between manual and automatic operation modes and permitting quick adjustment of conditions regarding the object. In this apparatus, a gear moving plate of a clutch mechanism is connected to the external gear of a zooming or focusing ring, a gear fixing plate of the clutch mechanism is connected to a zoom motor, and the gear moving plate is operated by a clutch operating motor via a coil spring and a moving gear to connect and disconnect the fixed plate. When the clutch mechanism is disconnected, a movable disk and a coil spring are enabled to freely rotate by a thrust bearing. By operating the clutch mechanism on the basis of an operational control signal for a zooming switch, switching between manual and electric operation modes is automatically accomplished. Further the manual operation torque of the zooming ring can be either adjusted with a volume control device or automatically maintained at a constant level. Further, if focusing is done when the zoom is set for manual operation, any variation in the angle of field due to a pumping phenomenon is corrected with a correcting circuit.