Image forming apparatus for executing developer replenishment control

An image forming apparatus, comprising:

• a latent image forming unit configured to form an electrostatic latent image on an image carrier based on an image signal;
• a development unit that includes a circulation mechanism configured to circulate developer along a circulation course in the development unit, and that is configured to develop the electrostatic latent image using the developer;
• a sensor configured to detect a toner density of the developer in the development unit and output a detected value corresponding to the detected toner density;
• a determination unit configured to determine a replenishment amount of toner to the development unit based on the detected value output by the sensor;
• and
• a replenisher unit configured to replenish the development unit with toner based on the replenishment amount determined by the determination unit,
• wherein the determination unit reduces a long period ripple of the detected value that occurs in accordance with a period of circulation of the developer along the circulation course by executing filter processing for reducing the long period ripple.