Patent ID: 7515844

Claim:
An image density control method which, when a two-component developer comprising a toner and a magnetic carrier on which the toner is held is carried on a developer carrier arranged opposing an image carrier, and said toner is used to develop an electrostatic latent image formed on the surface of the image carrier in a development region formed between said developer carrier and image carrier, employs a toner supply amount control device for keeping the toner density in said developer constant and a mechanism for determining a toner density control reference value to keep the development capability constant, and changes said toner density control reference value in accordance with an image coverage ratio of an output image, the method comprising: changing image forming conditions in accordance with the image coverage ratio of the output image to produce a constant image density; executing an operation for changing said image forming conditions at predetermined intervals when the image coverage ratio of said output image fulfills predetermined conditions; counting a number in which the image coverage ratio of said output image fulfills the predetermined condition; and determining said predetermined interval by a threshold number of said counting.