A light emitting system comprising: - a lighting device configured to provide light ; - a sensor configured to sense a distance parameter d between the lighting device and a user ; and - a control system configured to control one or more lighting properties of the light , wherein the lighting device , the sensor and the control system are configured to be comprised in a portable device , characterized in that the lighting device comprises a plurality of different light sources which are configured to provide light source light in different parts of the visible spectrum, the plurality of different light sources comprising two sources of blue light, which sources have a different overlap with a melanopic sensitivity curve as defined in the table in the detailed decription of the disclosure, and wherein the different light sources are individually controllable, the one or more lighting properties of the light are selected from (i) a spectral power distribution of the light , and (ii) a light intensity of the light , and the control system is configured to control (i) the spectral power distribution of the light and/or (ii) the light intensity of the light as a function of the distance parameter d for maintaining a melanopic illuminance at the user constant within a predetermined range, wherein the melanopic illuminance is calculated from an illuminance according to eq. 6 of the disclosure. - a lighting device configured to provide light ; - a sensor configured to sense a distance parameter d between the lighting device and a user ; and - a control system configured to control one or more lighting properties of the light , wherein the lighting device , the sensor and the control system are configured to be comprised in a portable device , characterized in that the lighting device comprises a plurality of different light sources which are configured to provide light source light in different parts of the visible spectrum, the plurality of different light sources comprising two sources of blue light, which sources have a different overlap with a melanopic sensitivity curve as defined in the table in the detailed decription of the disclosure, and wherein the different light sources are individually controllable, the one or more lighting properties of the light are selected from (i) a spectral power distribution of the light , and (ii) a light intensity of the light , and the control system is configured to control (i) the spectral power distribution of the light and/or (ii) the light intensity of the light as a function of the distance parameter d for maintaining a melanopic illuminance at the user constant within a predetermined range, wherein the melanopic illuminance is calculated from an illuminance according to eq. 6 of the disclosure. wherein the lighting device , the sensor and the control system are configured to be comprised in a portable device , characterized in that the lighting device comprises a plurality of different light sources which are configured to provide light source light in different parts of the visible spectrum, the plurality of different light sources comprising two sources of blue light, which sources have a different overlap with a melanopic sensitivity curve as defined in the table in the detailed decription of the disclosure, and wherein the different light sources are individually controllable, the one or more lighting properties of the light are selected from (i) a spectral power distribution of the light , and (ii) a light intensity of the light , and the control system is configured to control (i) the spectral power distribution of the light and/or (ii) the light intensity of the light as a function of the distance parameter d for maintaining a melanopic illuminance at the user constant within a predetermined range, wherein the melanopic illuminance is calculated from an illuminance according to eq. 6 of the disclosure. <EOS>