The method includes receiving an image of a subject via a lens of a camera, generating low-resolution images and high-resolution images repeatedly from the camera in response to a focus adjustment command inputted at a first timing point, displaying the low-resolution images as a preview image of the subject on a display, and storing at least one of the generated high-resolution images to be stored as a photo file of the subject in a memory in response to a photograph-taking command inputted at a second timing point behind the first timing point.