Why can a camera only focus on one distance at a time, and what occurs inside to change that focal distance? Does the same principle apply to our eyes?
In: Physics
Cameras change their focus by moving the lens closer to and farther away from the film (OK, charge-coupled devices these days). Your eyes change focus by changing the shape of the lens (flatter for distance viewing, rounder for close up). The narrower the aperture (light inlet) in the camera or the pupil of your eye, the deeper the field of view (depth of the distance in focus). In photography, using tiny apertures to get deeper fields of view also bring the problem of not getting as much light into the camera to make the picture. Long exposure times are needed to let in enough light to make a decent picture, so any movement will be just a blur in such photos.
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