Traditional rendering is based on the idea that light can be decomposed into three basic components: red, green and blue (RGB). In some areas this is a vast oversimplification of the physical reality; light exists on a continuous spectrum of wavelengths. Spectral rendering achieves better accuracy by taking that into account. The major drawback is that it cannot use widely available color data for surfaces such as photographs. The process of gathering usable spectral data is significantly more time- and resource-intensive.
Spectral upsampling is the process of extrapolating spectral information from RGB color data. This is possible because, in practice, spectral reflectivities, which describe how a surface interacts with incident light on a wavelength-by-wavelength basis, tend to fit relatively simple patterns. The goal would be to add support for several newly published algorithms to Colour, a color science library for Python. With the rising popularity of spectral rendering, the library would greatly benefit from the work.