An imaging apparatus of the present invention includes an optical lens unit of a photographic optical system; an imaging device for converting light received through the optical lens to electrical signals; a zooming device for changing a focal length of the photographic optical system; a zooming position detector for detecting a current zooming position; an A/D converter for converting analog image signals outputted from the imaging device to digital image signals; and a gradation sequence converter which converts a gradation sequence characteristic of the digital image signals by referring to a gradation sequence conversion table for converting the gradation sequence characteristic, wherein converting amounts of the gradation sequence conversion table are changed based on a current zooming position detected by the zooming position detector.