“Let’s say you go around your whole life and you see only pink, baby pink, a pastel pink,” said Ren Ng, an electrical engineer at the University of California, Berkeley. Then one day, someone shows you the most intense, vivid pink imaginable and calls it red. That is how Ng described the feeling of seeing “Olo,” a color so rich and new that it can’t be compared to anything in nature.
The finding of Olo, as reported by a team of scientists at UC Berkeley, has provoked as much wonder as disbelief among scientists. The hue, in vivid terms an intensely saturated blue-green, was created in a never-before-tried experiment using laser pulses to specifically stimulate isolated cone cells within the retina. Stimulation of the M cones cells detecting green wavelength the scientists evoked a visual sensation not accessible under natural light.
Ng, one of the five individuals tested during the study, said the colour was “jaw-dropping” and emphasized how new it is. “We predicted from the beginning that it would look like an unprecedented color signal, but we didn’t know what the brain would do with it,” he told The Guardian.
In attempting to understand the science behind Olo, you need to know about how the human eye perceives. There are three types of cone cells that make up the retina, the light-sensitive tissue at the back of the eye. They are S cones, for viewing short wavelengths (blue light); M cones, for viewing medium wavelengths (green light); and L cones, for viewing long wavelengths (red light). Natural light stimulates a mixture of these cones to generate the colors that we perceive. There is no natural source of light that is capable of stimulating the M cones selectively.
The researchers bypassed this limitation by virtue of assistance from a machine, also dubbed “Oz,” after L. Frank Baum’s *The Wizard of Oz*’s Emerald City. Oz employs mirrors, lasers, and optical equipment to illuminate individual M cones individually and leave the others in their resting state. The result is a color patch in the observer’s line of sight, twice the size of the Moon, and entirely out of gamut of color in normal viewing circumstances.
Even the name “Olo” itself was derived from the binary code 010, corresponding with the operative stimulation of M cones (1) but not of S and L cones stimulated (0). According to the team, this binary discrimination is the reason behind the world record-breaking color saturation.
While the breakthrough has been welcomed as a technological revolution, it has not been controversy-free. John Barbur, a vision scientist at London’s City University, responded that Olo is not a “new color” but a greener, more saturated green color which can only be generated under specific conditions. “It’s a more saturated green that can only be produced in a subject with normal red-green chromatic mechanism when the only input comes from M cones,” he told Taipei Times.
Other researchers are more focused on Olo’s phenomenology. “There is no way to convey that color in an article or on a monitor,” said Austin Roorda, who is a team member on the Berkeley project and a vision scientist. “The whole point is that this is not the color we see — it’s just not. The color we see is a version of it, but it absolutely pales by comparison with the experience of olo.”
The importance of this research extends well beyond discovering a new color. By teasing the retina at such a small scale, researchers think they will be able to understand better how the brain decides what something is looking at. It may lead to the next phase of brain-treating diseases like color blindness and retinal disease like retinitis pigmentosa.
Also, the study contradicts traditional color wisdom. Traditional color technology, such as screens and cameras, relies on spectral metamerism combining light wavelengths to simulate specific colors. The Oz system, however, employs spatial metamerism, controlling the spatial placement of light onto the retina to create colors unachievable through other methods.
While it is encouraging, the technology is in its infancy. Ng emphasized that Olo is an outcome of “basic science” and will not be seen on smartphone screens or virtual reality headsets anytime in the near future. “This is very, very far beyond VR headset technology,” he told BBC News.
For now, Olo is a private phenomenon savored by just five individuals. But its discovery makes available a whole new field of research into perception and vision available to scientific investigation and philosophical inquiry into the limits of human experience.
