A method for qualitatively evaluating material with at least one
identification characteristic, whose position can vary within an
expectation range designated by tolerance limits, involves the use of at
least one illuminating device, at least one photoelectric sensor and an
evaluating device. At least one background reference value and at least
one mask reference are stored in the evaluating device. The background
reference represents the characteristics of a printed image, particularly
the gray scale value, in at least one portion which surrounds the
identification characteristic. The mask reference represents the
geometrical contour of the identification characteristic. During
inspection of the printed material, differential image data is found, at
least from the expectation range, from the actual image data, and from
the background reference value in the evaluating device. The actual
position of the identification characteristic is subsequently derived in
the evaluating device.