Patent ID: 7251421

Claim:
An image forming apparatus, comprising: an image supporting body in which a latent image is formed; a developing device on which a plurality of developing units storing developers of the same color are detachably mounted; and control unit for controlling a printing operation in response to a print request in which the developers of the developing units are transferred to the latent image of the image supporting body to perform development, and for controlling a calibration operation in which a pattern of patches is developed on the image supporting body to perform calibration, wherein in the case where the number of calibration pages of a first developing unit, which is in use, is exceeded when the printing operation of the print request is executed, if there exists a second developing unit in which the number of calibration pages is not exceeded, the control unit executes the printing operation using the second developing unit, and if there does not exist the second developing unit in which the number of calibration pages is not exceeded, the control unit executes the printing operation using the first developing unit if the number of print pages of the print request does not exceed a predetermined threshold, and executes the calibration operation if the number of print pages of the print request exceeds the predetermined threshold, and thereafter executes a post-printing operation.