We show how illuminant and reflectance spectra can be accurately measured or separated, up to a multiplicative factor, at each pixel of a scene by using a CCD digital camera instead of a spectroradiometer. In order to obtain suitable spectra of both illuminants and reflectances in a scene, we may use a 6-channel measure from the digital 3-channel RGB camera. This is accomplished by taking two images of the scene, and using a colour filter during the second. No other practical or theoretical restrictions are needed to apply this separation algorithm, which is based on the validity of low-dimensional linear models for representing illuminant and reflectance spectra.
M. A. López-Álvarez, E. M. Valero, J. Hernández-Andrés, "Separating illuminant and surface reflectance spectra from filtered trichromatic camera measurements" in Proc. IS&T CGIV 2006 3rd European Conf. on Colour in Graphics, Imaging, and Vision, 2006, pp 370 - 373, https://doi.org/10.2352/CGIV.2006.3.1.art00076