1 The Director of Photography – an overview

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The motion picture
camera
Man has been beguiled by the movies for over a century now. One reason
might be that it takes a disarmingly simple piece of equipment, the
motion picture camera, to record images from the most fertile of our
imaginations.
In essence, a motion picture camera is a couple of boxes, one with a
lens on the front and a mechanism inside capable of dragging a length
of film down a specific distance at least 16 times a second, and the
other containing a suitable length of film to feed the mechanism with
space remaining to take up the film after exposure.
When the pictures from this device are projected by a similar mechanism
they give a valid representation of the original scene, with all the
movements contained therein correctly displayed in a realistic way.
The persistence of vision
Producing moving images from a length of still pictures relies on what
might be considered an aberration in the process of human vision. If
an image is flashed upon the retina of the eye the person sees that
image, briefly, in its entirety and then, over a short period, the image
stays with the person while growing fainter or decaying. If a second
image is flashed on the retina, soon enough the person will see the two
images as a continuous image without the first flash.
If there is movement in the interval between the flashing of the
images, the brain will perceive the difference between the two images
as continuous movement providing the time gap between the two
images is short enough. If a continuous stream of images is flashed
upon the retina in a quick enough succession, then the person will perceive
no flashing effects and will perceive the images as a continuous,
smooth motion.
The rate of image flashing at which the eye starts to perceive motion
is around ten flashes per second, though at this rate a flickering effect
will be very noticeable. Only at around 16 or 18 new images per second
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