An image forming apparatus forms a pattern image on a first printing medium and creates a first image processing condition for adjusting a tone characteristic based on a first luminance value. When performing the calibration using a second printing medium different from the first printing medium, the apparatus corrects, based on a luminance value of a background region of the second printing medium, a second luminance value output in accordance with light reflected by the second printing medium, and creates the first image processing condition based on the corrected second luminance value.