External ranging image pickup apparatus and ranging method

An image pickup apparatus configured to photoelectrically convert an optical object image formed by an image taking optical system to generate object image data, the apparatus comprising:

• a first detection unit configured to detect information corresponding to an object distance in each of plural areas, without through the image taking optical system;
• a second detection unit configured to detect a size and a position of a specific object area in the object image data, the specific object area being a part of the object image data corresponding to the specific object;
• and
• a controller configured to perform focus control of the image taking optical system on the basis of the information corresponding to the object distance detected by the first detection unit,
• wherein the controller is configured to acquire specific object distance information on a distance from the apparatus to the specific object, on the basis of the size of the specific object area detected by the second detection unit and information on a focal length of the image taking optical system, and to select, from the plural areas, an area where the information corresponding to the object distance to be used in the focus control is detected, on the basis of the specific object distance information and the position of the specific object area detected by the second detection unit.