PURPOSE:To quantitatively evaluate the quality of a copied image with taking the phenomena of a front edge omission and a rear edge omission into consideration by detecting the difference in density between the front end side and the rear end side of each group of parallel lines in a direction vertical to a parallel line of the copied image. CONSTITUTION:Each group of parallel lines of a copied image is scanned in cross section by using a densitometer having the detecting area in the scanning direction sufficiently smaller than the width of the finest or thinnest line in the standard area, thereby to measure the change of the density in the vertical direction. The density change at this time is plotted to the distance in the scanning direction, whereby a graph is obtained. Based on the obtained graph of the density distribution, the uniformness K of each group of parallel lines is calculated according to an equation K=(B+C)/(A+B) wherein A-C represent values of areas of peak parts sequentially measured from left when the maximum density is arranged at the leftmost in the graph. The uniformness K holds 0=K=1. As K is closer to 1, the group of parallel lines is copied more uniformly with the approximately same density at the front end and rear end thereof.
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