To provide a method for evaluating an image of a predetermined part of printed matter.
The image of the specific part in the printed matter is photographed with a camera having an electronic plane image sensor, selected with an electron evaluation unit and processed. In this case, an intensity signal obtained from a first specific section in the part is correlated with a reference data value showing an amount of a diffusion reflection strength of a light by an unprinted domain of the printed matter by calculation. At first, a white reference image is photographed and a basic reference data of a whole part is deduced from an intensity signal of the image. Every time an image of the predetermined part is evaluated, a corrected data is deduced from the intensity signal obtained from a second predetermined domain inside the part. Before correlating the intensity signal obtained from the first predetermined domain inside the predetermined part with the reference data by calculation, the reference data is calculated by correlation by calculation with a modified data of the basic reference data.