We’re so used to seeing special effects in feature films that an effect now has to be truly spectacular to excite interest. A recent example is the ‘bullet time’ effect used in the Wachowski brothers’ 1999 film The Matrix, where opponents suspended in space, fight each other in extreme slow m

This spark drum camera, devised by Lucien Bull in 1904, took 54 pairs of pictures at 2000 frames per second. Credit: NMPFT/Science & Society Picture Library

Visual effects supervisor John Gaeta achieved this effect by adapting the method employed a century earlier by Eadweard Muybridge. Gaeta set up 120 35mm motor-drive still cameras circling the action. He triggered these sequentially by computer, effectively recording images at 600 frames a second, even though each individual camera worked at only five frames a second. The resulting pictures were then copied in time sequence and combined with computer-generated backgrounds and bullet effects to produce the final high-speed circling slow motion shots.

Vinten HS 300 - the first high-speed camera capable of taking 300 frames per second using an intermittent mechanism. Credit: NMPFT/Science & Society Picture Library

Some fast-occurring events last for seconds; others just milliseconds. Different technology is needed to record each.  At the ‘low end’ are high-speed film cameras working at up to 360 frames a second, slowing time by a factor of 15. These are suitable for slow motion filming of wildlife or machinery. The cameras traditionally employed have faster versions of the shutter and intermittent claw mechanisms used in conventional film cameras. The film is pulled though the camera in a sequence of jerks using a mechanical claw inserted into the sprocket holes along the film edge. However, at higher speeds this can cause unsteadiness and even shred the film.

Other methods are used to achieve speeds of up to 40,000 frames a second.  In such cameras, the film moves continuously and a rotating glass prism behind the lens projects the image onto the film. As the prism rotates, a new image is recorded next to the previous one.  This type of camera is used widely in the study of vehicle crashes, packaging machinery, ballistics and rocketry. Much higher rates of up to 25 million frames a second are possible in rotating mirror cameras, which record images onto a short length of film in an arc.
Today, much high-speed research work has been taken over by video and digital cameras.  The first high speed video motion analysis cameras, capable of 120 frames a second, appeared in the 1970s and by 1980 Kodak introduced their SP2000 system that recorded up to 2000 frames a second.