| |MAY 20219tance. Try seeing your index finger by stretching your arm and by closing one eye at a time and then see with both the eyes open. This is called ste-reopsis or the binocluer vision, and is one of the important cues our brain processes to give us the perception of depth. Some of the other cues for the per-ception of distance are (1) Relative size of ratinal images. We know a per-son's approximate height. Now based upon the image of that person formed on the ratina the brain will `tell us' how far the person is. We do not not consciously think about the size, but our brain has learnt to calculate au-tomatically from image sizes, the dis-tances ofobjects when the dimensions are known from its database created all these years! (2) Moving parallax method. Try this experiment. You are reading this on a computer screen or on that of a mobile. Just adjust eyes such that you are able to see the back-ground wall or the tree also. Now move your head about an inch on either side. You will notice that the screen moves much faster than the background. This cue is processed by the brain and it determines that the screen is nearer to you than the background. (3) When very far distances are to be perceived, the strain on our eye muscles and pu-pil positions etc are calculated by our brain to give us a depth/distance per-ception.In short, the depth we `see' is ac-tually the perception our brain has managed to give us by processing various cues. Though we are three di-mensioned entities, each eye sees only in two dimensions and as a part of the evolutionary process and front faced eyes, our brain tricks us into believing that we see distance or depth. Consid-er this. Most predators have stereo-scopic vision with two frontal eyes to see how far the prey is. But the eyes of the prey are on the sides to get the maximum coverage of the surround-ings. They will not have binocular vi-sion to perceive depth.It is the binocular vision, or the ability of each of our eyes to see at dif-ferent angles and ability of the brain to process the two slightly differing images and give us the depth percep-tion which has opened up the `virtual 3D' space. Because, if, somehow, we trick each of our eyes to see an object with different angles, our brain has the capability to combine the images and produce a 3D image. But this is easier said than done. It requires an-other article of this size. as a part of the evolutionary process and front faced eyes, our brain tricks us into believing that we see distance or depth
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