Motion Blur
Motion blur is obviously essential to a realistic shot with agood amount of motion. It is the natural result of movement
that occurs while a camera shutter is open, causing
objects in the image to be recorded at every point from the
shutter opening to closing. The movement can be individual
objects or the camera itself.
Although it essentially smears layers in a composition,
motion blur is generally desirable; it adds to persistence
of vision, relaxes the eye, and is a natural phenomenon.
Aesthetically, it can be quite beautiful.
The typical idea with motion blur in a realistic visual effects
shot is to match the amount of blur in the source shot,
assuming you have reference; if you lack visual reference, a
camera report can also help you set this correctly.
A moving picture camera has a shutter speed setting that
controls the amount of motion blur. This is not the camera’s
frame rate, although the shutter does obviously have
to be fast enough to accommodate the frame rate. A typical
fi lm camera shooting 24 frames per second has a shutter
that is open half the time, or 1⁄48 of a second.
Motion blur occurs in your natural vision, although you
might not realize it—stare at a ceiling fan in motion, and
then try following an individual blade around instead and
you will notice a dramatic difference. There is a trend in
recent years to use extremely high-speed electronic shutters,
which drastically reduces motion blur and gives the
psychological effect of heightened awareness by making
your eye feel as if it’s tracking motion in this manner. This
seems to have started with live television sports coverage
and the use of extremely fast shutters for slow motion
replay cameras.
