Image forming apparatus and image forming method

An image forming apparatus, comprising:

• a photoconductor to form an electrostatic latent image;
• a special color developing device to develop the electrostatic latent image with a special color toner other than standard color toners on the photoconductor to form a special color toner image;
• an adhesion amount adjuster to adjust a special color toner adhesion amount by changing an application bias between the photoconductor and a developing sleeve of the special color developing device;
• a setting unit to set brightness of the special color toner;
• a developing-performance adjuster to adjust a developing performance of the special color developing device according to a setting value of the brightness of the special color toner set by the setting unit, wherein the developing-performance adjuster adjusts the developing performance of the special color developing device to a developing performance different from a developing performance set to each of standard color developing devices in adjustment of densities of the standard color toners;
• a mode setting unit to set one of a productivity first mode and an image-quality first mode on receipt of a mixed job including a plurality of jobs with different settings in the special color toner adhesion amount and a type of recording media;
• and
• a job analyzer to recognize the special color toner adhesion amount and the type of the recording media for each of the plurality of jobs in the mixed job,
• wherein, when the productivity first mode is set, the developing-performance adjuster executes adjustment of the developing performance of the special color developing device according to the special color toner adhesion amount, for a job having a maximum special color toner adhesion amount in the mixed job, and
• the adhesion amount adjuster adjusts the special color toner adhesion amount by changing the application bias of the special color developing device, for a job having a special color toner adhesion amount less than the maximum special color toner adhesion amount.