Gamma correction for apparatus using pre and post transfer image density

摘要

An image forming apparatus performs the gamma correction based on an image density on a photosensitive body or an intermediate transfer body. In the image forming apparatus, a test pattern generator unit generates a test image on the photosensitive body or the intermediate transfer body. A first density detector unit is provided in an upstream of a toner transfer section with respect to a rotation direction of the photosensitive body or the intermediate transfer body, and detects an image density on the photosensitive body or the intermediate transfer body. A second density detector unit is provided in a downstream of the toner transfer section with respect to the rotation direction of the photosensitive body or the intermediate transfer body, and detects the image density on the photosensitive body or the intermediate transfer body. A corrector unit corrects image data. A control unit calculates correction data for use in correcting the image data based on image density data outputted from the first and second density detector units to set the correction data in the corrector unit.