Patent ID: 7158730

Claim:
An image forming apparatus comprising: a plurality of process cartridges that integrally holds an image carrier and a developing unit that develops an electrostatic latent image formed on the image carrier to form a toner image, the process cartridges being compatible with each other; a plurality of installation sections in which the process cartridges are detachably installed, respectively; a carrier and a dummy toner stored in the developing unit of each of the process cartridges in a brand-new status to be installed in the installation sections; a plurality of toner supply units that supply a toner of one color from among a plurality of color toners, respectively, to the developing units of the process cartridges installed in the installation sections; and a transfer unit that transfers the toner image formed on the image carrier onto a medium to form an image, wherein the dummy toner is formed such that the dummy toner less contributes to formation of the image on the medium than the color toners, and each of the color toners is supplied to the developing unit from the toner supply units after the process cartridges in the brand new status are installed in the installation sections.