1. An image capturing apparatus comprising: an image capturing unit configured to capture an image of an object to output image data; a flash unit configured to apply light, to the object when the image capturing unit captures an image of the object; a holding unit configured to hold the image data output by the image capturing unit; a first image capturing control unit configured to cause the image capturing unit to capture an image of the object at a predetermined shutter speed, while the flash unit is applying no light; a second image capturing control unit configured to cause the image capturing unit to capture an image of the object at a shutter speed higher than the predetermined shutter speed, while the flash unit is applying no light; a third image capturing control unit configured to cause the image capturing unit to capture an image of the object at a shutter speed higher than the predetermined shutter speed, while the flash unit is applying light; a first position adjusting unit configured to perform a position adjustment between the image data obtained under the control of the first image capturing control unit and held in the holding unit, and the image data obtained under the control of the second image capturing control unit and held in the holding unit, thereby calculating a first displacement; second position adjusting unit configured to perform a position adjustment between the image data obtained under the control of the second image capturing control unit and held in the holding unit, and the image data obtained under the control of the third image capturing control unit and held in the holding unit, thereby calculating a second displacement; an image composing unit configured to obtain image data representing a composite image, by performing a position adjustment between the image data obtained under the control of the first image capturing control unit and held in the holding unit, and the image data obtained under the control of the third image capturing control unit and held in the holding unit, using the first and second displacements; and a saving unit configured to save, in a medium, the image data obtained by the image composing unit.