| 摘要 |
PROBLEM TO BE SOLVED: To make the forming state of a monochrome image excellent by eliminating the difference of gradation between when a monochrome image forming mode is set and when a color image forming mode is set concerning a color in which a monochrome image is formed. SOLUTION: In the case of making a lookup table for correcting output gradation in a black-and-white mode, a transfer carrying belt 216 is set to be in an inclined state, and only an image forming station 10a is actuated so as to form a test image consisting of 30 test patches only in BK on transfer material P. The density value of the test patch in BK is read from the material P, and the lookup table for correcting the output gradation is made so that an output gradation curve of each color may be matched with a target gradation curve selected by a user. The lookup table for correcting the output gradation in BK in the black-and-white mode and the lookup table for correcting the output gradation in a full color mode including the lookup table for correcting the output gradation in BK are made based on a result obtained by reading the test image formed in the respective modes, and processing for correcting the output gradation in the black-and-white mode is performed by referring to the lookup table for correcting the output gradation different from the lookup table for correcting the output gradation in BK in the full color mode. |
