In the 1920s, Erwin Schrodinger, better known for his famous dead-or-alive cat, turned his attention to colour. He believed that hue, saturation and lightness were not cultural inventions or habits of the mind. They were built into the mathematics of vision itself.
He sketched the framework. Then the trail went cold.
For nearly a hundred years, his model shaped scientific thinking, yet carried a silent flaw. Now, researchers at Los Alamos National Laboratory say they have repaired it.
THE GEOMETRY OF SEEING
To understand what the researchers fixed, it helps to begin with the eye itself.
Inside each human eye are three types of light-sensitive cells called cones. One reacts mostly to red light, one to green, and one to blue. Every colour we see is created by different combinations of signals from these three. Think of it like mixing three paints in varying amounts — except it all happens instantly in your brain.
Because colour depends on three signals, scientists describe it using three dimensions. Imagine a 3D map where every possible shade has its own location. Colours that look very similar sit close together. Colours that look very different are farther apart. This invisible map is called a “colour space”.
In the 19th century, mathematician Bernhard Riemann suggested that such spaces might not be flat like a sheet of paper. They might be curved, more like the surface of a globe. Decades later, Erwin Schrodinger applied this idea to colour.
He argued that hue (what we call red or blue), saturation (how intense it looks) and lightness (how bright or dark it is) are not random labels. They come directly from the shape of this 3D colour map.
It was a striking claim: colour experience built into mathematics itself, not shaped by culture or habit.
But there was a problem.
THE NEUTRAL AXIS PROBLEM
At the centre of every colour map lies a simple line: the greys. From black to white runs a path where there is no colour at all — only light and dark. Scientists call this the “neutral axis”.
Schrodinger’s system relied on this axis. It helped define how colours are arranged around it. Yet he never gave a precise mathematical definition of where that grey line sits inside the space. Without that, the entire structure rested on an assumption.
Roxana Bujack and her colleagues at Los Alamos National Laboratory in New Mexico set out to fix this gap. Instead of borrowing the old curved models as they were, they used more flexible geometry to let the colour space define its own centre.
From the internal structure of the system, they were able to pinpoint the neutral axis mathematically.
That single step stabilised the whole theory.
They also addressed a long-known visual quirk called the Bezold–Brucke effect, where increasing brightness can slightly change how a colour appears.
Instead of assuming colours shift in straight lines, the team calculated the most natural path within the curved space.
This also helped explain a familiar phenomenon but something we rarely notice: our eyes are extremely sensitive to small differences between similar shades, but once two colours are already very different, making them even more different does not make them feel proportionally more different to our eyes.
What began as abstract mathematics ends up describing something deeply familiar: the way your eyes see the world every single day.
WHY THIS MATTERS
The work, presented at the Eurographics Conference on Visualization, is not an abstract mathematical exercise.
Accurate colour models shape photography, film, digital design and scientific imaging. They help researchers interpret complex data, from climate maps to national security simulations.
A century-old theory first drafted in the shadow of early quantum mechanics has now been brought into the age of modern computation.
The cat may have made Schrodinger famous.
Colour, it turns out, may secure his other legacy.
