1. An image processing apparatus, comprising: an acquiring unit which acquires distance information corresponding to an object distance in a photographed image picked up by an image pickup element configured to receive light flux though a photographing lens; an image processing unit configured to perform an image processing for adjusting a focusing state of the photographed image, based on the distance information acquired by the acquiring unit; and a display control unit which displays, on a display unit, an image derived from the image processing by the image processing unit, wherein the image processing unit forms an image by adjusting the focusing state within a range corresponding to the object distance from a first distance to a second distance, and the image processing is performed based on an optical transmission characteristic between the photographing lens and the image pickup element.