Patent ID: 8373899

Claim:
A color image forming apparatus, comprising: a forming unit configured to form a plurality of mixed color patches that are different in a combination of gradation levels of a plurality of colors, the colors comprising yellow, magenta and cyan and to form a black patch; a detector configured to detect color of the plurality of mixed color patches and the black patch fixed on a transfer material by the forming unit; a calculator configured to obtain the gradation levels of yellow, magenta and cyan so that the color of each mixed color patch detected by the detector becomes similar to color of a corresponding black color of the black patch; and a specifying unit configured to specify an image forming condition related with a type of the transfer material or a type of print mode, wherein the forming unit forms the mixed color patches based on a first combination of gradation levels of yellow, magenta and cyan if the image forming condition specified is a first image forming condition, and the forming unit forms the mixed color patches based on a second combination of gradation levels of yellow, magenta and cyan different from the first combination of gradation levels of yellow, magenta and cyan if the image forming condition specified is a second image forming condition, wherein a color detection result of the mixed color patches formed by the first combination of gradation levels is able to encompass the corresponding black color on a color space, and a color detection result of the mixed color patches formed by the second combination of gradation levels is able to encompass the corresponding black color on a color space.