To record these movements inside intact insect eyes during light stimulation, the researcher had to build a bespoke microscope with a high-speed camera system. This microscopic light-sensor "twitching" is so fast that we cannot see it with our naked eye. But the University of Sheffield researchers found that photoreceptor cells underneath the lenses, instead, move rapidly and automatically in and out of focus, as they sample an image of the world around them. Unlike in the human eye, the thousands of tiny lenses, which make the compound eye's characteristic net-like surface, do not move, or cannot accommodate. However, researchers from the University of Sheffield's Department of Biomedical Science with their Beijing, Cambridge and Lisbon collaborators have now discovered that insect compound eyes can also generate surprisingly high-resolution images, and that this has much to do with how the photoreceptor cells inside the compound eyes react to image motion. As the lens in the human eye is quite large and the retinal photoreceptor array underneath it is densely-packed, the eye captures high-resolution images. By actively changing the lens shape, or accommodating, an object can be kept in sharp focus, whether close or far away. In contrast, the human eye has a single lens, which slims and bulges as it focuses objects of interests on a retinal light-sensor (photoreceptor) array the megapixel "camera chip" inside the eye. This is because their compound eyes typically consist of thousands of tiny lens-capped 'eye-units', which together should capture a low-resolution pixelated image of the surrounding world. Scientists have long believed insects would not see fine images.
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