A point sampled spectral distribution. Reconstruction with linear interpolation is suggested. Below the minimum specified wavelength, the amplitude associated with the minimum specified wavelength should be used. Above the maximum specified wavelength, the amplitude associated with the maximum specified wavelength should be used.
A jump discontinuity in the spectrum can be represented by using two data points with the same wavelength. In this case the value at that wavelength is the value of the latter pair (i.e. its right continuous).
Wavelengths should be described in ascending order.
spctrl 400 0.2 700 0.6 end % a reddish color
spctrl 400 0 400 1 500 1 500 0 end % blue box funtion primary [400,500)