Image forming apparatus including correction unit that corrects tone correction table

An image forming apparatus comprising:

• a forming unit configured to form an image on an image carrier;
• a holding unit configured to hold a reference table and a tone correction table that convert a plurality of input image data values into corresponding output image data values;
• and
• a correcting unit configured to control the forming unit to form a first test pattern including a plurality of images having different densities on the image carrier using the tone correction table, and correct the tone correction table by detecting densities of the plurality of images,
• wherein the correcting unit is further configured to correct the tone correction table by updating the tone correction table using the detected densities of the plurality of images and then interpolating the updated tone correction table using the reference table,
• wherein the reference table is generated using a second test pattern including a plurality of images having different densities, and a number of the images having different densities included in the second test pattern is greater than a number of the images having different densities included in the first test pattern.