Image forming apparatus utilizing a two-component developing apparatus with automatic toner replenishment and developer replacement

An image forming apparatus comprising:

• a plurality of latent image carrying bodies for carrying latent images;
• a plurality of developing of developing units each including means for supplying a developer to said respective latent image carrying body to develop said latent image on said latent image carrying body and means for accommodating the developer;
• at least one developer storage means for storing a fresh developer which is to be supplied to at least one of said developing units;
• and
• developer changing means for replacing the developer accommodated in said developing unit by the fresh developer stored in said developer storage means in accordance with an instruction that a replacement of developer is required,
• wherein said plurality of developing units develop with a plurality of different color developers including a black developer, said developer storage means stores a black developer which is to be supplied to a black developing unit which develops with the black developer, said developer storage means has a volume which is an integer multiple of the volume of the black developer which can be accommodated in said black developing unit.