| 摘要 |
PROBLEM TO BE SOLVED: To stabilize hue for a long period and to avoid abrupt fluctuation in hue.SOLUTION: Based on PASCALLUT(GLUT) for correcting intermediate half tone concentration, a multi-gradation patch (pattern image) consisting of a plurality of concentration level patterns is formed at an intermediate transfer belt 51. A concentration deviation amount between a concentration of each patch detected with a patch sensor 40 and a target concentration that is estimated from GLUT is corrected by using a feedback rate (correction coefficient). Compared with a multi-gradation patch control process which is executed at a first timing when a predetermined condition is met, or a predetermined time period has passed since a previous image formation, in a multi-gradation patch control process which is executed at a second timing, being relatively frequent, or every time a predetermined number of image formation operations are executed, the feedback rate is set low and the number of concentration levels constituting a pattern image is decreased. |
