1. An image capturing apparatus comprising: an image outputting unit configured to be capable of outputting an image with one of multiple resolutions; a face detecting unit configured to detect a face region of a person from an image output from the image outputting unit; an expression detecting unit configured to detect an expression of the person from an image corresponding to the face region; an instruction detecting unit configured to detect a shooting instruction given by a user; a setting unit configured to set an operation mode of the image capturing apparatus to a first operation mode using the expression detecting unit or to a second operation mode without the use of the expression detecting unit; and a control unit configured to control the image outputting unit to output an image with a second resolution, regardless of the operation mode of the image capturing apparatus, until the shooting instruction is detected by the instruction detecting unit, and wherein the control unit further controls the image outputting unit to output an image with a first resolution being higher than the second resolution and provides the image with the first resolution to the expression detecting unit, if the shooting instruction is detected by the instruction detecting unit and the operation mode of the image capturing apparatus is set to in the first operation mode by the setting unit, and wherein the control unit further controls the image outputting unit to output the image with the second resolution, if the shooting instruction is detected by the instruction detecting unit and the operation mode of the image capturing apparatus is set to the second operation mode by the setting unit.