Image forming apparatus which performs tone correction

An image forming apparatus comprising:

• an image forming unit configured to form an image on an image carrier based on an image signal;
• a holding unit configured to hold an image processing coefficients, each image processing coefficient of the image processing coefficients representing a relationship between an input density and an output density corresponding to a density of the image signal to determine the density of the image signal to be output to said image forming unit when performing tone correction;
• a reading unit configured to read a density of the image formed on the image carrier;
• and
• an updating unit configured to, when a plurality of measurement images are formed on the image carrier by said image forming unit and read by said reading unit, update an image processing coefficient based on the relationship between densities of the measurement images read by said reading unit and densities of image signals for forming the measurement images,
• wherein said updating unit is further configured to, when a maximum value of an output density of the image processing coefficients is smaller than a maximum value of the density of the image signal, form at least one first measurement image out of the plurality of measurement images in accordance with an image signal indicating a density higher than the maximum value of the output density of the image processing coefficients.