The invention relates to a control system (100) for an ambient light environment in a room in a hospital environment. The control system is configured to time and synchronize light effects of the ambient light environment (170, 190) in response to sensor signals (111-113) from patient location sensors (121) or other sensors (122,123) for detecting if a clinical instrument is activated, moved or taken into use or for detecting heart rate. Light effects may be used by the clinical personnel to improve quality and speed of the examination and to create a calming atmosphere for the patient. However, different light effects are required at different times and for different durations. Therefore, timing of the light effects relative to sensor signals may improve workflow and patient comfort.