>>12610004>what is colour, /sci/?The color of an object can be described physically via its spectral distribution function (a function whose integral over the interval [?,?+d?] represents the power per unit area of all light emitted by that object with wavelength in that range), but as the existence of a "visible spectrum" (approx. [380nm,700nm]) indicates, different f's may be indistinguishable to the human eye, so a "color space" as understood by laypeople is a different (and less refined) version of its full physical counterpart.
Experimental and biological evidence supports the theory of which says that this human colorspace is 3-dimensional (the colorspaces RGB, HSL, HSV, Lab, Luv etc. all have 3 parameters). Additionally, "Grassmann's laws of additive color mixture" state that this is mathematically a vector space, which basically means that we can represent the superposition of colors (i.e. their light sources) by addition of 3-dimensional vectors, with (0,0,0) as absolute darkness and scalar multiplication as color luminosity. (This explains the optical illusion in your picture: addition is commutative so the light reflected off the dress superposes with the ambient light to result in the "same" color.)
This representation can be modelled mathematically as a "color-matching function" converting a physical color f into its 3D-coordinates . In fact, such an m has been standardized and tabulated by the CIE (International Commission on Illumination) to define a "CIE 1931 color space", which is used in the SI definition of the candela.
Wyszecki and Stiles (1967) is a fairly accessible reference for all of this.
