In addition to supporting our visual perception of the world, light drives an array of reflex changes in physiology and behaviour, such as regulation of circadian rhythms, pupil constriction and hormone release. Traditionally, the sensory signal controlling such responses has been considered to be a simple measure of ambient light intensity, provided by melanopsin expressing retinal ganglion cell projections to a number of different subcortical brain regions (the suprachiasmatic nuclei, thalamic intergeniculate leaflet and the pretectum). Here I discuss some of our recent work that challenges this assumption, revealing unexpected sophistication in the sensory processing occurring within nuclei of the non-image forming visual system and suggesting potential new functions for communication between these brain regions