An apparatus for acquiring and evaluating an image of a predetermined
extract of a printed product removes the effects of scattered light to
improve the accuracy of image evaluation. The apparatus uses a camera
that has an electronic image sensor with a two-dimensional arrangement of
sensor elements. An aperture stop is arranged in the beam path of the
camera for shadowing a predetermined part of the image sensor. When an
acquired image is read from a part of the image sensor that is not
shadowed, corresponding readings from the shadowed portion of the sensor
are subtracted from the acquired image to obtain intensity signals
corrected for scattered light.