In order to regulate an illuminance, an actual value of a sensor (3) is queried, said value being dependent on the illuminance to be regulated and being regulated to a setpoint value. In a control step, an electronic computing device (11) determines an actuating step for an illuminant (2) on the basis of said actual value and a parameter value of a control parameter. The electronic computing device (11) determines a new parameter value of the control parameter for a subsequent control step on the basis of a first actual value which is received before the corresponding control step, and a second actual value which is determined after the corresponding control step.