You might remember the hullabaloo a couple of years ago surrounding the color of a certain dress – some claimed it was gold and others swore it was blue. The reason for the disagreement was due to what's known as "color constancy," whereby the brain attempts to identify the true color of an object even under changing light conditions. Cameras don't have this ability, but bees do, and the way they interpret color under varying light conditions could lead to more accurate image-processing in cameras, drones and robots.
For bees, the problem of color constancy is of vital importance. For the sake of their hive they need to be able to identify the color of their target flower under any lighting conditions, be it in a shaded forest or at dawn and dusk.
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A team of Australian scientists has unlocked the mystery of how bees can successfully identify colors across varying light conditions, and it involves three extra eyes on the top of their heads called ocelli. The function of these extra eyes has never been fully understood, but new research discovered each ocelli contains two upwards pointing color receptors that can accurately measure the color of ambient light. This allows bees to better identify the true color of an object and target their flower of choice across a variety of light conditions.
One of the researchers mapped the neural tracings from the ocelli and discovered that these receptors are connected to the parts of a bee's brain responsible for color perception. The only question remaining was how these two particular color receptors could allow the bees to interpret the entire color spectrum from red to ultraviolet?
The team built a mathematical model showing that if the ocelli focused on two specific wavelengths, ultraviolet and blue, they could cover most typical light levels a bee would encounter in their natural environment. This model accurately explains why bees cannot successfully interpret flower colors under yellowy artificial light and also why bees with blocked ocelli generally forage only in the middle of the day when light conditions are constant.
This research offers a clever, and simple, solution to achieving color constancy across our camera, robotic and drone systems. By incorporating two small, skyward pointing sensors in a camera to register the color of the ambient light, the researchers suggest that an object's true color could be identified across most light conditions.
As well as having benefits for general photography, the technique could prove extremely useful in industrial applications, bringing improvements in machine vision that would colored objects, such as ripe fruits or mineral-rich sands, to be identified easily across a variety of complex illumination conditions.
"The strength of this study lies in the combination of modeling, behavioural analysis and neuro-anatomy," says Professor Marcello Rosa, one of the authors on the study. "It shows how modern, interdisciplinary neuroscience can point to an elegant solution to classical problems in vision."
The team's study was published in the journal Proceedings of the National Academy of Sciences (PNAS).