A control unit for use in a lighting system that comprises at least one fixed light source and at least one portable light source , each providing a respective light output; the control unit comprising: a localization module configured to detect when the portable lighting device is within a predetermined vicinity of the fixed light source; and a controller configured to select between different roles for the portable light source with respect to the fixed light source, the roles comprising (i) an independent role in which the light output of the portable light source and fixed light source are controlled independently of one another, and (ii) a slave role in which the light output of the portable light source is adjusted in dependence on the light output of the fixed light source; wherein the controller is configured to switch to the slave role for the portable light source in response to said detection that the portable light source is within said predetermined vicinity of the fixed light source, wherein in the slave role the light output of the portable light source is adjusted to become more similar or dissimilar to the light output of the fixed light source in terms of one or more properties, and characterised in that the controller is configured to select between different behavior types, the behavior types comprising: a first behavior type wherein in the slave role the light output of the portable light source is adjusted to become more similar to the light output of the fixed light source in terms of one or more properties; and a second behavior type wherein in the slave role the light output of the portable light source is adjusted to become more dissimilar to the light output of the fixed light source in terms of one or more properties. a localization module configured to detect when the portable lighting device is within a predetermined vicinity of the fixed light source; and a controller configured to select between different roles for the portable light source with respect to the fixed light source, the roles comprising (i) an independent role in which the light output of the portable light source and fixed light source are controlled independently of one another, and (ii) a slave role in which the light output of the portable light source is adjusted in dependence on the light output of the fixed light source; wherein the controller is configured to switch to the slave role for the portable light source in response to said detection that the portable light source is within said predetermined vicinity of the fixed light source, wherein in the slave role the light output of the portable light source is adjusted to become more similar or dissimilar to the light output of the fixed light source in terms of one or more properties, and characterised in that the controller is configured to select between different behavior types, the behavior types comprising: a first behavior type wherein in the slave role the light output of the portable light source is adjusted to become more similar to the light output of the fixed light source in terms of one or more properties; and a second behavior type wherein in the slave role the light output of the portable light source is adjusted to become more dissimilar to the light output of the fixed light source in terms of one or more properties. a first behavior type wherein in the slave role the light output of the portable light source is adjusted to become more similar to the light output of the fixed light source in terms of one or more properties; and a second behavior type wherein in the slave role the light output of the portable light source is adjusted to become more dissimilar to the light output of the fixed light source in terms of one or more properties. <EOS>