PURPOSE: To prevent malfunction of white balance in the video processing system.

CONSTITUTION: When the on-operation of a power switch 28 of a video camera is detected and a change width of a luminous quantity detected by a Hall element 25 exceeds a specified value, a zoom motor 26 is driven to once shift a zoom lens toward the wide angle position, after the white balance is adjusted with the zoom lens set to the wide angle position, the zoom motor 26 is again driven to shift the zoom lens to a prescribed zoom position.