The theory based on the
camera analogy, however,
leaves everything about
perception still to be
explained. This becomes
evident as soon as we compare
the way the world appears to us
with the images of it projected
on our retinas. I have already
noted the discrepancy between
the shape of the object's image
and its perceived shape. In
addition to that, however, the
image of an object projected on
the retina changes
continuously as we move and as
our position with respect to the
object changes, yet we tend to
perceive the properties of
objects as constant under most
viewing conditions. In
watching people walking
toward or away from us, for
instance, we don't see them
physically enlarging or
shrinking, even though the
image on the retina does
exactly that. If we tilt our
heads to one side in gazing at a
building, it doesn't appear to
tilt, even though its retinal
image does so. As we go from
dim, indoor illumination to
bright sunlight, the intensity
of light reaching the eye can
vary by a factor of thousands.
Nevertheless, white surfaces
look white even in dim light,
and black ones look black even
in intense light. How can we
explain these constancies in
our perception? The camera
theory would lead us to predict
continuous change.