The majority of defects that may occur during the production process are "invisible" at the early stages of manufacture. These minute surface defects become visually perceptible later on, however, when subsequent work steps such as paint work have been completed. At that point in time, they can only be remedied using expensive corrective measures. To achieve a high surface quality with maximum cost optimization, a wide range of defect types needs to be detected. The reliable and, above all, timely detection and evaluation or classification of dents, bumps, sink marks, waviness, constrictions, cracks, etc. is necessary since the costs of removing these defects increase almost exponentially with the progress of work in the course of the production cycle (press shop, body shop, paint shop, final assembly).