> Not really: They used various other assumtions to get to the XYZ color 
> model, which were not part of the original tristimulus experiments (for 
> instance results from an experiment that tested for how people percieve 
> the brightness of spectral colors in relation to one another).

Well I don't know the details of exactly what experiments and calculations 
they conducted to end up with the colour matching functions, but today they 
are a standard to convert from a spectrum (which you can measure 
scientifically) to XYZ, which is the basis for all colour spaces.  If you 
are given a spectrum, you can get out only one possible XYZ colour, there is 
no reliance on any concept of "white" to make that conversion step.

> Given that "white" is what we humans /percieve/ as "white", that 
> equal-energy definition is not really reliable.

That isn't very scientific though, usually "white" in a strictly scientific 
way means equal energy across all relevant wavelengths (see "white noise" in 
audio).  The CIE colour matching functions were designed to give equal XYZ 
values when presented with a spectrum of "white" light such as this.

Obviously the human perception of what is "white" light varies greatly with 
the surrounding illumination (which often comes from the sun/sky), our 
psychological concept of what "should" be white etc, this is why various 
other whites are defined as standards.

I guess you could think up of an experiment in a completely dark room where 
you show a subject two near-white coloured light sources and ask them which 
is "whiter" than the other.  Repeat until you find "white".  Someone has 
probably done that already...

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