Your attention is immediately drawn to
the red car in this image, despite the
fact that it occupies only a small area of
the frame. This is due to many factors,
one of which is the fact that red is
associated with danger. Consequently,
we pay more attention to red than to
the colors around it.
Physical
Aspects of
Vision
Let’s discuss some basic physical aspects of vision
before describing how we use this information. As we
have seen, Light is made up of three primary colours..—
red, green, and blue—and this is basically how our eyes
see color. The light-sensitive cells within the eye are split
into two main types: rod-shaped and cone-shaped. The
rods are the most sensitive to light, but cannot
discriminate between different colors. The cones are less
sensitive to light, but contain chemicals that allow them to
see one of the three primary colors. The blue- and green-
sensitive rods equate very well to the colors that we think
of as pure primary colors, but the rods that we use to see
red light are only sensitive to light that we would consider
to be orange. The information given by these three types
of rod is sent to our brain, which interprets the information
to give us a mental picture of the scene. So, while our
eyes play a major part in the physical aspects of vision, it
is our brain that determines what we see.