A lighting commissioning system comprising: a plurality of luminaires (L1, L2), each luminaire co-located with a light source and a light sensor; a controller configured to selectively control the light sources to emit light and to receive signals from the light sensors representative of light sensed thereby; and a memory accessible to the controller; characterized in that the controller is configured to execute a first phase of commissioning by executing an algorithm to calculate at least one reflectance value associated with a reflecting surface which lies between a local area of a luminaire and a local area of a neighboring luminaire (A1/2), and to store the one or more reflectance values in the memory, and a second phase of commissioning in which the reflectance values are accessed by the controller for converting light sensed by each light sensor from an emitting light source into a measure of distance between the emitting light source and each light sensor; wherein the controller is configured in the first phase of commissioning to carry out the steps of: activating a light source of a first luminaire; measuring light reflected from a local area to a light sensor on the first luminaire; determining a reflection coefficient for the local area; and repeating the steps for at least one neighboring luminaire to thereby determine at least one additional reflection coefficient for a local area under the neighboring luminaire; and executing an algorithm on the reflection coefficients to calculate the at least one reflectance value associated with the reflecting surface which lies between the local area of the first luminaire and the local area of the at least one neighboring luminaire. a plurality of luminaires (L1, L2), each luminaire co-located with a light source and a light sensor; a controller configured to selectively control the light sources to emit light and to receive signals from the light sensors representative of light sensed thereby; and a memory accessible to the controller; characterized in that the controller is configured to execute a first phase of commissioning by executing an algorithm to calculate at least one reflectance value associated with a reflecting surface which lies between a local area of a luminaire and a local area of a neighboring luminaire (A1/2), and to store the one or more reflectance values in the memory, and a second phase of commissioning in which the reflectance values are accessed by the controller for converting light sensed by each light sensor from an emitting light source into a measure of distance between the emitting light source and each light sensor; wherein the controller is configured in the first phase of commissioning to carry out the steps of: activating a light source of a first luminaire; measuring light reflected from a local area to a light sensor on the first luminaire; determining a reflection coefficient for the local area; and repeating the steps for at least one neighboring luminaire to thereby determine at least one additional reflection coefficient for a local area under the neighboring luminaire; and activating a light source of a first luminaire; measuring light reflected from a local area to a light sensor on the first luminaire; determining a reflection coefficient for the local area; and repeating the steps for at least one neighboring luminaire to thereby determine at least one additional reflection coefficient for a local area under the neighboring luminaire; and executing an algorithm on the reflection coefficients to calculate the at least one reflectance value associated with the reflecting surface which lies between the local area of the first luminaire and the local area of the at least one neighboring luminaire.