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No, the CIE standard observer is not the same as the responsivities of cone cells in the eye. That article you linked describes how it was arrived at: 1. Match monochromatic (narrow wavelength band) light sources of each wavelength with three particular monochromatic lights (called “R”, “G”, “B”), in some cases needing to add some of one of those three to the monochromatic source in order to get the two sides to match – this is a “negative” component. This process results in three (r(λ), g(λ), b(λ)) functions of wavelength. 2. Take three linear combinations of those three functions and call them (x(λ), y(λ), z(λ)), such that (a) the y(λ) function is approximately the same as the photopic luminance function as best it could be computed at the time, (b) all three of x, y, and z had only positive values, and (c) integrating each of the three yields the same value, so that an equal-energy stimulus will have the same X, Y, and Z values. The red receptors in the human eye do not really have this kind of spike in response in the lower end of the spectrum. * * * However, “red” the “psychological primary” or “unique hue” does have some violet/blue in it. Any monochromatic red light source is a bit on the orange side. |