You might ponder this, so put one of the fingers from each of your hands in front of your face
and try to estimate the distance between them. This is difficult, and I am sure you would agree
that your measurement would not be very accurate. Now put your fingers very close together.
You can still tell that they are apart even when the distance between them is tiny. So human
vision can distinguish relative distance well, but is poor for absolute distance. Computer vision
is the other way around: it is good for estimating absolute difference, but with relatively poor
resolution for relative difference. The number of pixels in the image imposes the accuracy of
the computer vision system, but that does not come until the next chapter. Let us start at the
beginning, by seeing how the human vision system works.
In human vision, the sensing element is the eye from which images are transmitted via the optic
nerve to the brain, for further processing. The optic nerve has insufficient bandwidth to carry all the