I am writing an article on #thedress. I have read that this illusion is partially explained by daylight locus, and I do not fully understand this idea.
I know that it represents the distribution of natural light color spectrum, and that it must be influenced by latitude and season. But I do not fully understand what is represented in the x and y axis of the graphic and how these curves are obtained. Neither have I understood the role that this this concept has in #thedress perception.
Best regards.
Julio.
I think the main confusion about color in this discussion comes from the unsharp defined question which color is asked for. Its a difference if you ask for the color of a surface, that is defined by the reflectance spectrum of the surface alone. And you could ask for the color a surface appears in a certain lighting situation. The spectrum reflected or scattered from a surface is then the product of the illumination spectrum times the reflectance spectrum of the surface. If you illuminate a white surface with a mainly blue sky-light than the absolute observed spectrum will be also sky-blue. A further contribution to factor in here is the "white balance" our eye and brain does and most cameras do. This white balance compensates the illumination spectrum, it more or less divides the actually received spectrum by the illumination spectrum. So even in a blue-heavy sky-illuminated situation a white surface can appear white, because the camera or eye knows, that the illumination is biased.
The central core of the #thedress is, that if you don't state which color you are asking for, you must get different answers.
-color (reflectance spectrum) of the surface without lighting
-color (spectrum) of the scattered light in a certain biased illumination
-apparent color after white balance
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