Rooms are lit up differently by the incidental daylight and the artificial lighting of the lamps. Not all surfaces in the rooms, e.g. walls, floor, and
furniture reflect the light that falls on them in the same manner. Accordingly, even though there is an exactly calibrated constant lighting control in
daily operation, deviations to the set target value may occur. These deviations may be up to +/- 100 lx should the current ambient conditions in the
room, and accordingly the reflection properties of the surfaces (paper, persons, reorganized or new furniture), differ significantly from the original
ambient conditions at the time of calibration. Deviations may also occur if the light sensor is influenced by direct or reflected light falling on it, which
is not influenced or only slightly influenced by the surfaces in the detection range of the light sensor.