In colorimetry, the irradiance spectrum is weighted with the luminosity function

Question

In colorimetry, the irradiance spectrum is weighted with the luminosity function to obtain the perceived luminosity, and the tristimulus sensitivity functions to obtain the perceived RGB-representation.

How do these functions (just one scalar for each wavelength) relate to each other?

I only found these weighting functions (as numerical arrays) in the matlab package pspectro. There however, the sensitivity function for gamma (= green) is completely identical to the luminosity function, which seems odd. Is it correct?

Explanation / Answer

Better late than never?

Yes, what you found in the Matlab package is correct. The luminosity function is the exactly the same curve as the green part of the three XYZ Tristimulus Curves used in modeling human perception of color.

Note the XYZ color space is not the same as the RGB color space of a display; XYZ represents the totality of what humans can perceive, and any RGB color space is inherently a subset of XYZ.

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