Patent ID: 7209672

Claim:
An image forming apparatus, comprising: a latent image carrier capable of carrying thereon an electrostatic latent image; a developing unit having a plurality of cartridges which are freely mounted to and removed from said developing unit and which contain toner of a specific color; and a controller which performs a printing operation to selectively position one of the plurality of cartridges mounted to said developing unit at a development position and to develop the electrostatic latent image on said latent image carrier using the toner in the cartridge positioned at the development position, wherein said controller defines N (M>N≧2) cartridges out of M (M≧3) cartridges mounted to said developing unit as selected cartridges and conducts a print preparatory operation prior to the printing operation only on the selected cartridges, the print preparatory operation conducted on the selected cartridges in order to enable the printing operation by means of the selected cartridges.