To provide a calibration method and the like capable of specifying an image conversion condition excellent in the reproducibility of the density of a proofing object when the proofing object is created by DDCP by using binary area gradation images for printing by FM screening.

The calibration method for performing gradation correction to the binary area gradation image using the FM screening is provided with a step of estimating the number of dots or the average size of the dots per unit image of the standard binary area gradation image employing the FM screening; a step of estimating an effective dot area rate per unit image by using the output product of the binary area gradation image; and a step of calculating a correction amount of the binary area gradation image by using the number of dots or the average size of the dots and the effective dot area rate.