Sun, Apr 20, 2025 page5

• Scientists claim to have found never before seen color

  HUE KNEW? Researchers fired laser pulses into their eyes and saw a color similar to turquoise, which they named ‘olo,’ that is beyond the natural range of the naked eye

  • The Guardian
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  After walking the Earth for a few hundred thousand years, humans might think they have seen it all. Not according to a team of scientists who claim to have experienced a color no one has seen before.

  The bold — and contested — assertion follows an experiment in which researchers in the US had laser pulses fired into their eyes.

  By stimulating individual cells in the retina, the laser pushed their perception beyond its natural limits, they said.

  Their description of the color is not too arresting — the five people who have seen it call it blue-green — but that does not fully capture the richness of the experience, they said.

  “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,” University of California, Berkeley electrical engineer Ren Ng said. “It was jaw-dropping. It’s incredibly saturated.”

  The researchers shared an image of a turquoise square to give a sense of the color, which they named “olo,” but stressed that the hue could only be experienced through laser manipulation of the retina.

  “There is no way to convey that color in an article or on a monitor,” said Austin Roorda, a vision scientist on the team. “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.”

  Humans perceive the colors of the world when light falls on color-sensitive cells called cones in the retina.

  There are three types of cones that are sensitive to long, medium and short wavelengths of light.

  Natural light is a blend of multiple wavelengths that stimulate long, medium and short cones to different extents.

  The variations are perceived as different colors. Red light primarily stimulates long cones, while blue light chiefly activates short cones. However, medium cones sit in the middle and there is no natural light that excites those alone.

  The Berkeley team set out to overcome the limitation.

  They began by mapping a small part of a person’s retina to pinpoint the positions of their medium cones. A laser is then used to scan the retina. When it comes to an medium cone, after adjusting for movement of the eye, it fires a tiny pulse of light to stimulate the cell, before moving on to the next cone.

  The result, published in Science Advances, is a patch of color in the field of vision about twice the size of a full moon.

  The color is beyond the natural range of the naked eye, because the M cones are stimulated almost exclusively, a state natural light cannot achieve. The name olo comes from the binary 010, indicating that of the long, medium and short cones, only the medium cones are switched on.

  The claim left one expert bemused.

  “It is not a new color,” City St George’s, University of London vision scientist John Barbur said. “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 medium cones.”

  The work had “limited value,” he said.

  The researchers believe the tool, named Oz vision after the Emerald City in the L. Frank Baum books, would help them probe basic science questions about how the brain creates visual perceptions of the world.

  However, it might have other applications. Through bespoke stimulation of cells in the retina, researchers might learn more about color blindness or diseases that affect vision, such as retinitis pigmentosa.

  Would the rest of the world get the chance to experience olo for themselves?

  “This is basic science,” Ng said. “We’re not going to see olo on any smartphone displays or any TVs any time soon. And this is very, very far beyond VR headset technology.”
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