An image forming apparatus includes: an image bearing member; an image forming unit configured to form a toner image on the image bearing member based on an image input signal; a detection sensor configured to detect a detection image at multiple density levels, which is formed by the image forming unit; a correction unit configured to correct image output characteristics of the image forming unit with respect to the image input signal, based on a detection result of the detection sensor; and a change unit configured to change the density levels at which the detection image is formed so that the detection image is preferentially formed in a density area of a large absolute value of a rate of change of slope of the image output characteristics.