Naked Science Forum
General Science => General Science => Topic started by: Heereyven on 15/07/2008 10:00:25
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Heereyven asked the Naked Scientists:
How can cameras zoom in on an object, but our eyes can't?
What do you think?
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There is probably no advantage in having Zoom Eyes. You can see 'enough' detail in distant objects to determine whether they are good to eat or a threat. Each animal has its own criteria for judging this. Ducks and rabbits have more or less 360o vision but they don't need the forward, binocular, arrangement of a predator which needs good distance judgement to latch its teeth on a moving prey with accuracy.
For Humans, there is an effective 'zoom' function - more of a software / conceptual zoom. The central area of vision has much greater acuity so, when we need to scrutinise something, we 'look at it' with this area. We get a wide, general view using the rest of our retina. More important for peripheral vision is the detection of changes and movement - which is just what we have. Our system is far more sophisticated than a straightforward Zoom Lens - it is an 'intelligent' system.
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Even when we are looking steadily at something our eyes are constantly moving and the image is 'steadied' in the brain. The amount of movement is very small but you can see it in someone else (check they don't mind you staring at them). This movement would become a problem as you zoomed in on something because in zooming in you are narrowing your field of view and whereas the brain can cope with a few degrees of eye movement in a wide field of view, a couple of degrees eye movement in a narrow field of view of, say ten degrees, would probably induce motion sickness. This is why it is so difficult to hold high-powered binoculars or telescope steady just by hand - as the magnification increases, the same small amounts of movement cover larger proportions of the field of view.
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I've often wondered what we would see if our eyes were like the Chameleon's that seem able to move independently of one another and whether this means it has a different kind of optical chiasma from ourselves.
Also, what effect this would have on its binocular vision as this appears to work when both eyes are focused on the same spot - and it seems to need this when it winds in those inverts it feeds on.
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Must be pretty weird but I can imagine a wide 2D field of view narrowing and a 3D region sort of 'popping' up when the eye views overlap. That's just purely my imagination though, and not based on any scientific fact.