The easiest and most intuitive way to illustrate and understand the design
and operation of the human eye has been to parallel its structure to a
photographic camera or, in more recent times, a videocamera. This might
sound paradoxical, because it is probably closer to the truth to assume
that optical design of the photocamera was derived in some way from the
eye's structure. The role and relevance of constitutive elements such as
the cornea, iris, crystalline lens, and retina gain immediate insight from
comparison with their technical counterparts (objective, diaphragm, focus
adjustment, and photosensitive film), which are familiar to most people.
With the advent of electronic photosensor matrices (digital cameras),
the comparison can be pushed further, not only through the obvious
equivalence between detector pixels and retinal photoreceptors, but also
including on-board signal preprocessing to parallel with neuroretinal
filtering and summation.
Use of the eye-camera comparison is not simply confined to the naïve
description of the eye provided by encyclopedias or, at a higher level,
by introductory optics manuals, but it is also exploited for meaningful
scientific investigations. Even the purely optical characterization of
ocular performances recalls what happens with
reflex photocameras, where different objectives can be coupled to different
camera bodies containing sensory and driving circuitry.