Please inspect Figure 1. Figure 1. The CIE 1931 Chromaticity Diagram. If this diagram gives you a headache, this web log is for you. I will never show it to you again. If you’re a color-technology professional, or training to become one, this web log is intended to give you a headache. Method and Language I want to establish facts about the geometry of what we call color using only elements of perception that are uncontroversial and widely shared. But before any geometric description can be justified, there is first a need to establish that geometry—at all—is an appropriate vehicle for exploring these facts. Human beings can look at light, compare what they see, and reliably report whether two appearances differ. They can order colors, notice smooth variation, and detect when small changes become noticeable. None of this requires a theory of vision, empirical practices, nor agreement about underlying mechanism. It is part of lived experience. Read More →