1. An image processing method for obtaining an out-of-focus image by using a plurality of images, the method comprising: capturing a first image, a second image, and a third image, which are captured with different focuses for the same subject and background, wherein the first image is an image in which the subject is focused, the second image is an image in which the background is focused, and the third image is a super-macro image in which no part of the image is focused; setting a subject portion and a background portion by using the first and second images, wherein the setting comprises: generating a first difference of Gaussian (DoG) image and a second DoG image by applying a DoG filter to each of the first and second images; comparing radio frequency components in mask regions of the first and second DoG images with each other, wherein the mask regions respectively include reference pixels that are located at corresponding positions of the first and second DoG images; generating a single binary-coded image by representing the reference pixels as a first brightness value when the radio frequency component of the first DoG image is greater than that of the second DoG image, and representing the reference pixels as a second brightness value when the radio frequency component of the second DoG image is greater than that of the first DoG image; and correcting error pixels included in the generated binary-coded image; and combining the first image for the subject portion and the third image for the background portion with each other to obtain an out-of-focus image.