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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?

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Welcome to Physics.SE! It looks like you may have a solid physics question here, but the way it's currently phrased, it'll probably get flagged as off topic. You may want to consider explaining the physics concept that's troubling you, rather than the specific code/function/package. If it's the code you want help with, StackExchange is definitely more suitable. – Kitchi Mar 19 '13 at 17:24
This is kind of an interesting one, because based on the package description, it seems to be partly about color spaces (which is a computer science topic) and partly about photometry (which lies at the interface of biology and physics, but is probably fine here). I think @Kitchi might be right that there is a solid physics question, but as its written now, it comes across as being about Matlab to a large extent. LearnOPhile, any chance you could edit your question to explain more about the physical functions this package models, so people don't have to click through to the documentation? – David Z Mar 20 '13 at 2:49
Thanks for your feedback! I edited and clarified the question and, most importantly, tagged it in colorimetry (= "visable-light"). Hoping for answers, but the physics.SE community seems really very good anyways! – LearnOPhile Mar 20 '13 at 9:11
Also, we answer these kinds of questions in SciComp… :) – Nick Mar 20 '13 at 9:16

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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