1. An image capturing apparatus, comprising: a main image capturer performing an image capturing operation on a target object according to a detection focusing distance; an auxiliary image capturer disposed adjacent to the main image capturer, and the auxiliary image capturer performing a plurality of focusing operations on the target object according to a plurality of focusing distances, and generating a plurality of image contrast values; a controller coupled to the main image capturer and the auxiliary image capturer to control the main image capturer and the auxiliary image capturer, and the controller selecting one of the focusing distances to be the detection focusing distance according to the image contrast values; a touch screen configured to receive input corresponding to the target object; and a lookup table coupled to the controller, wherein the controller generates a main focusing distance from the detection focusing distance after all of the focusing operations are completed according to the lookup table, and the main image capturer focuses on the target object according to the main focusing distance and performs the image capturing operation, and the detection focusing distance is smaller than the main focusing distance, wherein the image capturing apparatus is a handheld device, and wherein a view range of the main image capturer is smaller than a view range of the auxiliary image capturer.