  Light plays a key role in the regulation of different physiological
processes, through several visual and non-visual retinal phototransduction
channels whose basic features are being unveiled by recent research. The
growing body of evidence on the significance of these effects has sparked a
renewed interest in the determination of the light field at the entrance pupil
of the eye in indoor spaces. Since photic interactions are strongly
wavelength-dependent, a significant effort is being devoted to assess the
relative merits of the spectra of the different types of light sources
available for use at home and in the workplace. The spectral content of the
light reaching the observer eyes in indoor spaces, however, does not depend
exclusively on the sources: it is partially modulated by the spectral
reflectance of the walls and surrounding surfaces, through the multiple
reflections of the light beams along all possible paths from the source to the
observer. This modulation can modify significantly the non-visual photic inputs
that would be produced by the lamps alone, and opens the way for controlling
-to a certain extent- the subject's exposure to different regions of the
optical spectrum. In this work we evaluate the expected magnitude of this
effect and we show that, for factorizable sources, the spectral modulation can
be conveniently described in terms of a set of effective filter-like functions
that provide useful insights for lighting design and light pollution
assessment. The radiance field also provides a suitable bridge between indoor
and outdoor light pollution studies.
