1. An image forming apparatus comprising: (a) first and second electrically chargeable members; (b) first processing means to form a primary electrostatic latent image on said first chargeable member; (c) second processing means to form a secondary electrostatic latent image on said second chargeable member based on said primary electrostatic latent image, to develop said secondary electrostatic latent image, and to transfer the thus developed image onto an image transfer material; (d) means for detecting a visible image forming capability of one of the electrostatic latent images; and (e) means for controlling in response to an output from said detecting means, at least one of said first processing means and said second processing means so as to form a developed image of a predetermined image density.