1. An image capturing apparatus comprising: an image capturing unit configured to generate image signals by converting an optical image of a subject into electrical signals on a pixel-by-pixel basis, the image capturing unit capable of outputting image signals with multiple resolutions; a face detecting unit configured to detect a face region of a person from image signals output from the image capturing unit; an expression detecting unit configured to detect an expression of the person from image signals corresponding to the face region, among the image signals output from the image capturing unit; a determination unit configured to determine whether the image capturing apparatus is operated in a first operation mode using the expression detecting unit or in a second operation mode without the use of the expression detecting unit; and a control unit configured to control the image capturing unit to output image signals with a first resolution higher than a second resolution and to provide the image signals with the first resolution to at least the expression detecting unit of the face detecting unit and the expression detecting unit in a case in which the determination unit determines that the image capturing apparatus is operated in the first operation mode, wherein the second resolution is a resolution with which image signals are to be output by the image capturing unit in a case in which it is determined that the image capturing apparatus is operated in the second operation mode.