A tomography method for generating a computed tomography (CT) image, including generating a first tomography image based on first raw data corresponding to a received X-ray comprising acquired photons; determining second raw data by generating a second tomography image having an increased resolution in comparison with the first tomography image and performing forward projection on the second tomography image; determining third raw data based on a first parameter, the first raw data, and the second raw data; and generating a third tomography image based on the third raw data, wherein the determining of the third raw data may be based on information about a distribution of the acquired photons, the information being included in at least one from among the first raw data and the second raw data.