A controller comprising: presence detection logic, calibration logic, and an input for receiving a reading from a light sensor representing a sensed light level. The presence detection logic is for detecting presence events based on a presence sensor, and is configured to indicate a set-point to operate at least one lighting device in dependence on a positive detection of presence. The calibration logic is for performing a calibration operation, which is performed by causing a light output of the lighting device to change between a first, lower level and a second, higher level, and by and calibrating the set-point based on the reading from the light sensor under influence of the first and second levels. The calibration logic is configured to trigger this calibration operation in response to the positive detection of presence.