| 摘要 |
An image forming apparatus includes a first developing device for developing an electrostatic image with a developer including toner and carrier; a second developing device for developing an electrostatic image with a developer including toner which is different from the toner and carrier; first supplying means for supplying the toner into the first developing device; second supplying means for supplying the toner into the second developing device; toner content detecting means for detecting a toner content in the developer in the first developing device; image density detecting means for detecting an image density of a reference toner image formed using the first developing device and the second developing device; and control means for operating the apparatus selectively in a first mode in which an image forming operation is carried out using only the first developing device out of the first developing device and the second developing device, and the first supplying means supplies the toner using at least a detection result of the toner content detecting means, and a second mode in which an image forming operation is carried out using the first developing device and the second developing device, and the first supplying means and the second supplying means supply the toner using at least a detection result of the image density detecting means, wherein a frequency of formations of the reference toner images when the toner is supplied using both of the detection results of the toner content detecting means and the image density detecting means, in the first mode, is lower than a frequency of formations of the reference toner images in the second mode.
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