WORLD VIEW. How apprehensive animals their environment? Differently from us. Bees indeed perceive ultraviolet (UV) and reptiles, infrared radiation both areas inaccessible to us. Now, cameras and cameras are now calibrated for human vision. Good news for the film industry, which however is not without its problems for researchers working on animal vision. For how to study more closely the color change from green crab, or the subtle color variations in which some nocturnal birds camouflage their plumage in the environment, when perceptions of these species differ from ours? To remedy this recurring problem, researchers at the University of Exeter (UK) have developed an open-source software (ie free, the source code is freely available and adaptable) for calibrating photographs to highlight the specifics of the vision of various animals. Their work led to publication in Methods in Ecology and Evolution.
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But how to simulate the animal vision, based on images from digital sensors? Jolyon Troscianko, lead author, said: “Digital cameras are a powerful tool for measuring the colors.” Still, it was hitherto difficult to obtain reliable color reproductions of animal vision. “Our software allows us to calibrate the images to match the animal vision, and the compare to human vision of a scene. ” In practice, these images are reconstructed by stacking several layers: the photographer captures the same scene several times, using filters on the camera lens, some leave such pass only the visible spectrum, and other only ultraviolet. These different layers are then concatenated into a single file in RAW format (see box below). Then used algorithms to process photography to highlight the characteristics of the vision of the animal studied.
RAW FORMAT. This photographic format contains all the information obtained by the sensor, not a compressed image as the traditional JPG. It allows to easily alter contrast, colors, brightness retrospectively, as would a film photographer in his laboratory.
The advantage? Make visible what is invisible to human eyes (such as UV), or otherwise qualify colors that are too bright for our eyes. Most mammals do indeed perceive as blue and yellow, trichromisme (perception of blue, yellow and red) is the preserve of humans and some monkeys. The device is already used by a group of British researchers sensory ecology. “We hope that other scientists will use this software freely available, and that will be useful in their analysis” , still says Jolyon Troscianko. For tinkerers at heart, the software is freely downloadable at this address.
Lizards Gallotia galloti: left, human vision, and right version where UV rays were highlighted. The dimorphism of males (blue spots) is much more obvious in the light of the vision that these reptiles have the ultraviolet spectrum. / © Jolyon Troscianko
ROUTE GUIDED. In 2013, Dassault Systèmes technology had resulted in a guided tour of Paris with hawk eyes, cat, dog, rat, or even bees. The software behind this spectacular immersive experience (see video below), however, is nothing open-source, and was primarily intended for public demonstration. For the scientist, a more realistic imaging of animal vision will deepen the understanding of many ecological phenomena, including camouflage and biomimicry.
© DassaultSystemes / YouTube
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