Camera vs. The Human Eye
The individual components of the eye work in
a manner similar to a camera. Each part plays a vital role in providing
clear vision. So think of the eye as a camera with the
behaving much like a lens cover. As the eye's main focusing element, the
cornea takes widely diverging rays of light and bends them through the
the dark, round opening in the center of the colored iris. The
act like the aperture
of a camera.
Next in line is the lens
which acts like the lens in a camera, helping
to focus light to the back of the eye.
The very back of the
eye is lined with a layer called the retina which acts very much
like the film of the camera. The retina is a membrane containing
photoreceptor nerve cells that lines the inside back wall of the eye. The
photoreceptor nerve cells of the retina change the light rays into
electrical impulses and send them through the optic nerve to the brain
where an image is perceived.
Because the light rays
cross while going through the cornea, the retina reads the image upside
downóbut the brain readjusts so you stay properly oriented. It is believed that for the first few
days, babies see everything upside-down. This is because they have not
become used to vision.
Your brain CAN be retrained though. In one psychological study,
participants were asked to wear inverting lenses - lenses that invert the
image BEFORE they get to your eye, so that when your eye inverts it, it's
right side up. At first, everything appeared upside-down to the
participants. But, after a few days, people began to report that
everything appeared right side up! As a second part of the study, the
people were asked to take the glasses off. Because they were now used to
the lenses, their NORMAL vision appeared upside-down!! Within a day,
though, their vision returned to normal. The reason you don't see
everything upside-down, then, is simply because it's easier to think about
right side up!