Abstract: A color copying apparatus includes a color image sensor, an image information signal processing unit, and a color printer. The apparatus converts the three color component signals from the color image sensor into a luminance signal component and color difference signal components. At least one of the luminance signal component and the color difference signal components is subject to a nonlinear conversion. For density conversion between an input image and an output image, the luminance signal component is subject to a nonlinear conversion in a nonlinear conversion circuit.

Abstract: The invention provides an apparatus for forming a multicolor image, comprising a photoconductive drum which comprises a conductive substrate, and a photoconductive layer and a transparent insulating layer, a first charger to perform primary charging, a first light source to expose the entire surface of the photoconductive drum, a second charger to secondarily charge the transparent insulating layer at the second polarity, a second light source to emit light, an amount of which is controlled to have two levels in accordance with first and second color image data, a first developing unit to develop the first color image, a third light source to perform a second entire-surface exposure of the photoconductive drum, and a second developing unit to develop the second color image.