Method to operate an access system

The method involves determining an ambient brightness around a motor vehicle (FZ) using a brightness sensor (HS). The presence of an authorized mobile identification transmitter (IDG) in an approach area around the motor vehicle is examined, where the brightness sensor is designed as an ambient light sensor. An activation signal for an illumination source of the motor vehicle is output when the ambient brightness drops below a predetermined value and the presence of the identification transmitter is detected in the approach area. An independent claim is also included for an access arrangement for a vehicle.