Los Alamos Team Supplies Missing Neutral Axis in Schrödinger’s 1920s Color Perception Model

Scientists at Los Alamos National Laboratory have finished a mathematical definition of how humans perceive colour by establishing the neutral axis that Erwin Schrödinger left undefined in the 1920s. Roxana Bujack led the team that used geometric principles to define hue, saturation and lightness solely through the colour metric.

The work shows these three qualities are intrinsic properties of the metric rather than products of culture or learning.

"What we conclude is that these colour qualities don't emerge from additional external constructs such as cultural or learned experiences but reflect the intrinsic properties of the colour metric itself," Bujack said. The researchers presented the findings at the Eurographics Conference on Visualization.

The project extends a 2022 paper the same laboratory published in the Proceedings of the National Academy of Sciences.

Human colour vision depends on three cone-cell types sensitive to red, blue and green, forming a three-dimensional space that can be analysed mathematically. In the nineteenth century Bernhard Riemann proposed that such spaces have curved geometry, a concept later developed into Schrödinger's model. Schrödinger never formally defined the neutral axis, the grey line running from black to white.

Because his definitions of hue, saturation and lightness all rely on a colour's position along that axis, the omission left the framework incomplete. The Los Alamos team supplied the missing definition using only the geometry of the colour metric and moved beyond traditional Riemannian mathematics to do so.

They also corrected shortcomings in the original model, including the Bezold-Brücke effect in which changes in light intensity alter perceived hue.