A spectrum element describes a wavelength-dependent parameter. They are used for describing light sources, material properties, instrument sensivities, ... Spectra may have different units depending on their context of use : transmission spectra are unit-less, while source spectral radiance is given in W·m−2·sr−1·m−1. There are several spectrum types. For instance, tabulated spectrum uses only tabulated user data. Other spectrum types follow physical laws (such as blackbody which uses Planck's law) and are defined by a few parameters.
This is the most simple spectrum type with a uniform, wavelength-independent value.
The preset spectrum type accesses the spectra stored in the program, given a spectrum name.
This spectrum type takes tabulated spectral values as input
This spectrum type corresponds to a square shaped spectrum, with a constant "top" value between two wavelengths, and a "base" value otherwise.
This spectrum type corresponds to Cauchy's equation for dielectrics.
This spectrum type allows adjusting spectral properties with RGB values as in traditional computer graphic software.