PURPOSE: To obtain a copy which is free of ground staining and character blurring by scanning an original and classifying its density by levels, and controlling copying density parameters on the basis of a level corresponding to the largest area.

CONSTITUTION: A scanning carriage 11 makes a preliminary scan prior to slit exposure and a read sensor part 14 measures the density of the original 2. A fixed sensor 21 scans the center part of the original and moving sensors 22 and 23 driven by a wire 15 displaced according to scanning scan the original slantingly. The size of the original is detected from the difference in reflectivity between an original pressure plate and the texture of the original. The reflectivity levels of the original are classified by several stages and the lengths of areas belonging to the respective levels are calculated. The level with the maximum length and the darkest value and mean value of the original density are used to control the luminosity of an exposure lamp.