The present invention discloses an image taking apparatus which can control image deterioration caused by the image size of an attached lens apparatus and image generating region of an image pickup element not corresponding. The image taking apparatus has an image pickup element which photoelectrically converts an object image formed by the attached lens apparatus; an image producing section which produces recording image data to be recorded based on an output from the image pickup element; and a controller which judges an image size of the attached lens apparatus and changes an image producing region for producing the recording image data within a light receiving region of the image pickup element based on the judged image size.