A normal motion picture is
filmed and played back at 24 frames per second, while television
uses 25 frame/s (PAL) or 29.97
frame/s (NTSC). High speed cameras can film up to 250,000
frame/s by running the film over a rotating prism or mirror
instead of using a shutter, thus reducing the need for stopping
and starting the film behind a shutter which would tear the film
stock at such speeds. Using this technique one can stretch one
second to more than 10 minutes of playback time (super slow
motion). The fastest cameras are generally in use in scientific
research, military test and evaluation, and industry. An example
of an industrial application is crash testing to better document
the crash and what happens to the automobile and passengers
during a crash. MythBusters often use high speed cameras to see
their tests in slow motion.
A problem for high speed cameras is the needed exposure for the
film, so one needs very bright light to be able to film at
40,000 frame/s sometimes leading to the subject of examination
being destroyed because of the heat of the lighting.
Even higher speed imaging is possible using specialized
electronic charge-coupled device (CCD) imaging systems which can
achieve speeds of up to or in excess of 25 million frames per
second. All development in high speed cameras is now focused on
digital video cameras which have many operational and cost
benefits over film cameras.
Recent
advances in the form of image
converter devices are able to
provide temporal resolutions of
less than 50 picoseconds,
equivalent to over
20,000,000,000 frames per
second. These instruments
operate by converting the
incident light (consisting of
photons) into a stream of
electrons which are then
deflected onto a photoanode,
back into photons, which can
then be recorded onto either
film or CCD.
Such high frames rates are
unnecessary in the field of TV &
Feature Films, where a maximum
frame rate of 4000 frame/s
(frames per second) and an image
resolution of 1920 x 1080 pixels
would suffice (this resolution
equates to "Sony HD" which is
sufficiently high enough to suit
transfer to film for showing in
cinemas). Until recently
however, image quality - such as
dynamic range and light
sensitivity - have limited the
application of digital video
cameras. As of January 2008, the
best high speed digital video
camera available is the Phantom
HD capable of 1000 frame/s at
1920 x 1080 pixels with a 14-bit
colour bit depth.
