Image forming apparatus which performs tone correction

An image forming apparatus includes: holding means for holding image processing coefficients, each of which representing a relationship between an input density and an output density of an image signal output to image forming means; and an updating means forupdating an image processing coefficient based on the relationship between densities of measurement images and densities of image signals for forming the measurement images. The updating means, 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, forms at least one first measurement image in accordance with an image signal indicating a density higher than the maximum value of the output density of the image processing coefficients.