IMAGE FORMING APPARATUS

PROBLEM TO BE SOLVED: To shorten time required for a correcting operation, while keeping accuracy in correcting the gradation characteristic of a formed image. SOLUTION: An image forming apparatus includes: a gradation pattern forming section for forming a gradation pattern on an image carrier; a density detecting means for detecting the density of a gradation pattern; an imaging-condition adjusting means for adjusting an imaging condition based on the result of detection obtained by a density detecting means; an input/output characteristic correction signal forming means for forming an input/output correction signal based on the result of the detection of a gradation pattern of a type different from the gradation pattern used by the imaging-condition adjusting means; an input/output characteristic altering means for altering an input/output characteristic; a control-timing determining means having first control for correcting the density of a solid portion by use of the imaging-condition adjusting means and second control for correcting gradation by use of the input/output characteristic altering means and configured to determine the execution timings of the two types of the control; and an image area ration limiting means for limiting the width of the image area ratio of each of the patches of the gradation pattern formed in the second control. COPYRIGHT: (C)2011,JPO&INPIT