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do time

Time-lapse

[tahym-laps]

Time-lapse photography is a cinematography technique whereby each film frame is captured at a rate much slower than it will be played back. When replayed at normal speed, time appears to be moving faster and thus lapsing. Time-lapse photography can be considered to be the opposite of high speed photography.

Processes that would normally appear subtle to the human eye, such as motion in the sky, become very pronounced. Time-lapse is the extreme version of the cinematography technique of undercranking, and can be considered a borderline form of stop motion animation.

History

Some classic subjects of timelapse photography include:

  • cloudscapes and celestial motion
  • plants growing and flowers opening
  • fruit rotting
  • evolution of a construction project
  • people in the city

The technique has also been used to photograph crowds, traffic, and even television. The effect of photographing a subject that changes imperceptibly slowly, is to create a smooth impression of motion. A subject that is changing quickly already is transformed into an onslaught of activity.

The first use of time-lapse photography in a feature film was in Georges Méliès' motion picture Carrefour De L'Opera (1897). Time-lapse photography of biologic phenomena was partially pioneered by F. Percy Smith in 1910 and Roman Vishniac from 1915 to 1918. Time-lapse photography was further pioneered in a series of feature films called Bergfilms, including (Mountain films) by Arnold Fanck, in the 1920s, including The Holy Mountain (1926).

But no filmmaker can be credited for popularizing time-lapse more than Dr. John Ott.

Ott's initial "day-job" career was that of a banker, with time-lapse movie photography, mostly of plants, initially just a hobby. Starting in the 1930s, Ott bought and built more and more time-lapse equipment, eventually building a large greenhouse full of plants, cameras, and even self-built automated electric motion control systems for moving the cameras to follow the growth of plants as they developed. He even time-lapsed his entire greenhouse of plants and cameras as they all worked, a virtual symphony of time-lapse movement. His work was featured on an episode of the request TV show, You Asked For It in the late 1950s.

Ott also discovered that the movement of plants could be manipulated by varying the amount of water plants were given, and varying the color-temperature of the lights in the studio, with some colors causing the plants to flower and other colors causing the plants to bear fruit. Ott even discovered ways to change the sex of plants merely by varying the light source color-temperature.

By using these techniques, Ott time-lapse animated plants "dancing" up and down in synch to pre-recorded music tracks.

His cinematography of flowers blooming in such classic documentaries as Walt Disney's Secrets of Life (1956), pioneered the modern use of time-lapse on film and television. Ott wrote a book on the history of his time-lapse adventures, My Ivory Cellar (1958).

Ott's experiments with different colored lighting systems and their effects on the health of plants led to experiments with colored lights on the health of animals, then humans, then on individual cells, using time-lapse micro-photography. Ott discovered that only a full spectrum of natural light (including natural amount of infra-red AND ultra-violet) worked to entirely promote full physical and mental health in plants, animals and humans. A second book detailing these experiments followed, Exploring the Spectrum (1973). Ott-Lights are sold at lighting stores worldwide.

A major refiner and developer of time-lapse is the Oxford Scientific Film Institute in Oxford, United Kingdom. The Institute specializes in time-lapse and slow-motion systems, and has also developed camera systems that could go into (and move through) impossibly small places. Most people have seen at least some of their footage which has appeared in TV documentaries and movies for decades.

PBS's NOVA series aired a full episode on time-lapse (and slow motion) photography and systems in 1981 titled Moving Still. Highlights of Oxford's work are slo-mo shots of a dog shaking water off himself, with close ups of drops knocking a bee off a flower, as well as time-lapse of the decay of a dead mouse.

The first major usage of time-lapse in a feature film was Koyaanisqatsi (1983). The non-narrative film, directed by Godfrey Reggio, contained much time-lapse of clouds, crowds, and cities lensed by cinematographer Ron Fricke. Years later Ron Fricke produced a solo project called "Chronos" shot on IMAX cameras which is still frequently played on discovery HD. The most recent film made entirely in time lapse photography is Nate North's film Silicon Valley Timelapse, which also holds the distinction of being the first feature length film shot almost entirely in 3 frame HDR.

Countless other films, commercials, TV shows and presentations have included time-lapse.

For example, Peter Greenaway's film A Zed & Two Noughts featured a sub-plot involving time-lapse photography of decomposing animals and included a composition called "Time-lapse" written for the film by Michael Nyman. More recently, Adam Zoghlin's time-lapse cinematography was featured in the CBS television series Early Edition, depicting the adventures of a character that receives tomorrow's newspaper today. David Attenborough's 1995 series, The Private Life of Plants, also utilised the technique extensively.

Terminology

The frame rate of time-lapse movie photography can be varied to virtually any degree, from a rate approaching a normal frame rate (between 24 and 30 frames per second) to only one frame a day, or even a week, or more, depending on the slowness of the subject.

The term "time-lapse" can also apply to how long the shutter of the camera is open during the exposure of EACH frame of film (or video), and has also been applied to the use of long-shutter openings used in still photography in some older photography circles. In movies, both kinds of time-lapse can be used together, depending on the sophistication of the camera system being used. A night shot of stars moving as the Earth rotates requires both forms. A long exposure of each frame is necessary to allow the dim light of the stars register on film, with lapses in time between frames providing the actual movement when viewed at normal speed.

As the frame rate of time-lapse approaches normal frame rates, these "mild" forms of time-lapse are sometimes referred to simply as fast motion or (in video) fast forward. This type of borderline time-lapse resembles a VCR in a fast forward ("scan") mode. A man riding a bicycle will display legs pumping furiously while he flashes through city streets at the speed of a racing car. Longer exposure rates for each frame can also produce blurs in the man's leg movements, heightening the illusion of speed.

Two examples of both techniques are the running sequence in Terry Gilliam's The Adventures of Baron Munchausen (1989) in which Eric Idle outraces a speeding bullet, and Los Angeles animator Mike Jittlov's impressive 1980 short and feature-length film, both titled The Wizard of Speed and Time, released to theaters in 1987 and to video in 1989.

When used in motion pictures and on television, fast motion can serve one of several purposes. One popular usage is for comic effect. A slapstick style comic scene might be played in fast motion with accompanying music. (This form of special effect was often used in silent film comedies in the early days of the cinema; see also liquid electricity.)

Another use of fast motion is to speed up slow segments of a TV program that would otherwise take up too much of the time allotted a TV show. This allows, for example, a slow scene in a house redecorating show of furniture being moved around (or replaced with other furniture) to be compressed in a smaller allotment of time while still allowing the viewer to see what took place.

The opposite of fast motion is slow motion. Cinematographers refer to fast motion as undercranking since it was originally achieved by cranking a handcranked camera slower than normal. Overcranking produces slow motion effects.

How time-lapse works

Film is often projected at 24 frame/s, meaning that 24 images appear on the screen every second. Under normal circumstances a film camera will record images at 24 frame/s. Since the projection speed and the recording speed are the same the images onscreen appear to move normally.

Even if the film camera is set to record at a slower speed, it will still be projected at 24 frame/s. Thus the image on screen will appear to move faster.

The change in speed of the onscreen image can be calculated by simply dividing the projection speed by the camera speed.

mathrm{perceived speed} = frac{mathrm{projection frame rate}}{mathrm{camera frame rate}}timesmathrm{actual speed}

So a film that is recorded at 12 frames per second will appear to move twice as fast. Shooting at camera speeds between 8 and 22 frames usually falls into the undercranked fast motion category, with images shot at slower speeds more closely falling into the realm of time-lapse, although these distinctions of terminology have not been entirely established in all movie production circles.

The same principles apply to video and other digital photography techniques, however until very recently video cameras have not been capable of recording at variable frame rates.

Time-lapse can be achieved with some normal movie cameras by simply clicking individually frames manually. But greater accuracy in time-increments and consistency in the exposure rates of successive frames are better achieved though a device that connects to the camera's shutter system (camera design permitting) called an intervalometer. The intervalometer regulates the motion of the camera according to a specific interval of time between frames. Some intervolometers can also be connected to motion control systems that move the camera on any number of axes as the time-lapse photography is achieved, creating tilts, pans, tracks, and trucking shots as the speeded up motion is viewed. Ron Fricke is the primary developer of such systems, which can be seen in his short film Chronos (1992) and his feature film Baraka (1992, released to video in 2001).

Short Exposure vs. Long Exposure Time-lapse

As first mentioned above, in addition to modifying the speed of the camera, it is also important to consider the relationship between the frame interval and the exposure time. This relationship essentially controls the amount of motion blur present in each frame and it is, in principle, exactly the same as adjusting the shutter angle on a movie camera. This is also known as "Dragging the shutter."

A film camera normally records film at twenty four frames per second. During each 24th of a second the film is actually exposed to light for roughly half the time. The rest of the time it is hidden behind the shutter. Thus exposure time for motion picture film is normally calculated to be one 48th of a second (1/48 second, often rounded to 1/50 second). Adjusting the shutter angle on a film camera (if its design allows) can add or reduce the amount of motion blur by changing the amount of time that the film frame is actually exposed to light.

In time-lapse photography the camera records images at a specific slow interval such as one frame every thirty seconds (1/30 frame/s). The shutter will be open for some portion of that time. In short exposure time-lapse the film is exposed to light for a normal exposure time over an abnormal frame interval. So for example the camera will be set up to expose a frame for 1/50th of a second every 30 seconds. Such a setup will create the effect of an extremely tight shutter angle giving the resulting film a stop-animation or clay-mation quality.

In long exposure time-lapse the exposure time will approximate the effects of a normal shutter angle. Normally this means that the exposure time should be half of the frame interval. Thus a 30 second frame interval should be accompanied by a 15 second exposure time to simulate a normal shutter. The resulting film will appear smooth.

The exposure time can be calculated based on the desired shutter angle effect and the frame interval with the equation:

mathrm{exposure time} = frac{mathrm{shutter angle}}{360^circ}timesmathrm{frame interval}

Long exposure time-lapse is less common because it is often difficult to properly expose film at such a long period, especially in daylight situations. A film frame that is exposed for 15 seconds will receive 750 times more light than its 1/50th of a second counterpart. (Thus it will be more than 9 stops over normal exposure.) A scientific grade neutral density filter can be used to alleviate this problem.

Time-lapse camera movement

As also earlier mentioned, some of the most stunning time-lapse images are created by moving the camera during the shot. A time-lapse camera can be mounted to a moving car for example to create a notion of extreme speed.

However to achieve the effect of a simple tracking shot it is necessary to use motion control to move the camera. A motion control rig can be set to dolly or pan the camera at a glacially slow pace. When the image is projected it could appear that the camera is moving at a normal speed while the world around it is in time lapse. This juxtaposition can greatly heighten the time-lapse illusion.

The speed that the camera must move to create a perceived normal camera motion can be calculated by inverting the time-lapse equation:

mathrm{actual speed} = frac{mathrm{camera frame rate}}{mathrm{projection frame rate}}timesmathrm{perceived speed}

Baraka was one of the first films to use this effect to its extreme. Director and cinematographer Ron Fricke designed his own motion control rigs that utilized stepper motors to pan, tilt and dolly the camera.

A panning timelapse can also be easily and inexpensively achieved by using a widely available telescope Equatorial mount with a Right ascension motor (* 360 degree example using this method). Two axis pans can be achieved as well with contemporary motorized telescope mounts (* link)

A variation of these are rigs that move the camera DURING exposures of each frame of film, blurring the entire image. Under controlled conditions, usually with computers carefully making the movements during and between each frame, some exciting blurred artistic and visual effects can be achieved, especially when the camera is also mounted onto a tracking system of its own that allows for its own movement through space.

The most classic example of this is the slit-scan opening of the stargate sequence toward the end of Stanley Kubrick's 2001: A Space Odyssey (1968), created by Douglas Trumbull.

Related techniques

HDR Time-lapse

The most recent development in time-lapse cinematography is a convergence of High dynamic range imaging (photographic technique) and multi frame time-lapse. One of the first experiments was an 11 second series completed in un-automated form by Nicholas Phillips on July 8, 2006 link Modern time-lapse enthusiasts have started to follow suit as of May 2007. Ollie Larkin (work) and Jay Burlage (work) have both successfully shot and processed HDR time-lapse footage in High definition, with motion control, using DSLR cameras. The first example of this technique in a full length film can be seen in Silicon Valley Timelapse (2008).

References

  • ICP Library of Photographers. Roman Vishniac. Grossman Publishers, New York. 1974.
  • Roman Vishniac. Current Biography (1967).
  • My Ivory Cellar John Ott. (1958)
  • Exploring the Spectrum John Ott. (1973)

External links

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