| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that prevents the image degradation being the side effect, while utilizing an advantage of performing a monochromatic print only by an image carrier unit (black station) corresponding to this, thereby contributing to enlargement of the use flexibility of a user. Ž<P>SOLUTION: The apparatus calculates an average full color ratio y and an average image area ratio x that have been output after receiving a monochromatic job, which are substituted for expression y-(5-x)=A. If A>0 at this point, the job is present out of a problem occurrence area, so that an image is output by a normal monochromatic control in which a color photoreceptor drum is separated from an intermediate transfer belt. If A≤0, the job is present in the problem occurrence area, thereby the monochromatic image is output by a full color. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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