1. An image capturing apparatus comprising: an image capturing unit for capturing an image, the image capturing unit including an image sensor; and a controller connected to the image capturing unit, wherein the controller is configured to: obtain a background image with depth information, position a three-dimensional (3D) virtual image in the background image based on the depth information, the 3D virtual image being used in identifying a 3D space position and/or a 3D posture of a target object to be photographed, determine a difference between the 3D virtual image in the background image and the target object in a live preview image of the image capturing unit while the image capturing unit is positioned to capture a scene corresponding to the background image, and control the image capturing unit to photograph the target object automatically when the difference becomes less than a predetermined threshold.