Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for performing actions based on a determined relative composition of light. In some implementations, data representing an amount of ambient light detected within the portion of the property by a light sensor located at the portion of the property is initially obtained. Data indicating (i) a shape of an optical spectra for a natural light source, and (ii) a shape of an optical spectra for a non-natural light source is then obtained. A relative composition of the ambient light detected within the portion of the property is determined. An estimated amount of natural light within the portion of the property is then determined. In response, the amount of light output by one or more light sources located at the portion of the property is adjusted.