Slow motion

The slow motion is a special effect , realized during the shooting or in deferred, and specific to the cinema and the television, which consists in filming a subject by accelerating the rate of shooting (in English overkranking ) so that the movement of the subject is slowed to the projection. In the sound cinema, at the standard projection rate, fixed at 24 frames per second, to slow down the movements of the subject filmed twice, the camera that took the picture must turn at 48 frames per second. For a slow motion of three times, the camera must reach 72 frames per second, and so on.

The slow-motion is an ultra slow motion effect taken image by image on shorter durations, characteristic technique of animation , but also basic technique of photography .

The opposite process is called accelerated , it consists in filming a subject by decreasing the rate of shooting (in English underkranking ) so that the movement of the subject proceeds faster to the projection. Ex: At 8 frames per second when shooting, the rhythm will be boosted 3 times at the standard frame rate of 24 frames per second.

Principles to remember: acceleration of the camera = slow motion motion projection; slowdown of the camera = accelerated motion in projection.

History

In 1894 , it was by trying to solve a problem of brightness that the operators of the first movies, William Kennedy Laurie Dickson and William Heise , employed by Thomas Edison , discover the slow motion . At the time, the adjustable diaphragm , as we know it today, does not exist yet. To measure the amount of light that impresses the film, the Kinetic does not have any device. Faced with the problem of overexposure, posed during shooting when the sun is too powerful, Dickson and Heise have the idea to accelerate the speed of the camera. Rather than make it run at the normal pace of silent cinema, ie at 16-18 frames per second, they shoot at 30, 35 or 40 frames per second depending on the sun, which shortens the exposure time light-sensitive layer, thus avoiding over-exposure of the image. Of course, the consequence of this acceleration of the 35-40 frames per second film roll, also causes a real slowing down of the filmed action, “a second of real life pass under the eyecup of the Kinetoscope in roughly two seconds, the viewing device operating at the fixed frame rate of 18 frames per second. The movement is slowed down by the same amount, that is to say about twice 1 . ” It was during the filming ofCaïcedo, king of acrobatics , who was practicing his art on a cable stretched outside Edison’s shooting studio , the Black Maria , so in full sun that was thus discovered slow motion. Shot at 40 frames per second, Caïcedo’s acrobatics are correctly exposed and metamorphose into a real idle air ballet.

Later, in 1895 , Louis Lumière and his engineer Charles Moisson took the precaution of providing the Cinématographe with various caches to dispose of in front of the lens, offering round openings of varying size, and to give it the possibility of increasing and reduce the width of the closing area of ​​its shutter, which will allow their ingenious machine to record whatever the brightness.

In the 1920s , some films, budgets permitting, show trains that derail or are dragged into the fall of a bridge. This is how in Le Mecano de la “General”, a car leaves the track and shatters on the ballast, a locomotive collapses into the river by a burning bridge that yields under the weight of the convoy. All this is very expensive. And the slow motion has been used throughout the history of cinema, before digital virtual effects, as a trick allowing at a lower cost to give the illusion of a normal mass in the shots on models. The most sought after were the images of ships splitting water from the specialized basins that any studio had, the shipwrecks, the explosions on board … Low-budget films showed miniature trains rolling, derailing or falling in ravines. The movement of the model was filmed at frame rates between 60 and 80 frames per second. The slow motion obtained made it possible to believe – little or much – that the model was an object with normal dimensions; by slowing down the action, we obeyed the equation: distance = speed x duration. The explosion (dispersion), or the fall (terrestrial attraction), are made at the same speed with a model or an object of real size. If we increase the duration by a slow motion, we increase at the same time the distance traveled by the object or its debris, giving the illusion of a larger object. The quality of a scene of displacement or destruction of a model was once again the budget devoted to this trick, the most accurate models and made of materials imitating to perfection those who constitute the real object, gave the best effect we obeyed the equation: distance = speed x duration. The explosion (dispersion), or the fall (terrestrial attraction), are made at the same speed with a model or an object of real size. If we increase the duration by a slow motion, we increase at the same time the distance traveled by the object or its debris, giving the illusion of a larger object. The quality of a scene of displacement or destruction of a model was once again the budget devoted to this trick, the most accurate models and made of materials imitating to perfection those who constitute the real object, gave the best effect we obeyed the equation: distance = speed x duration. The explosion (dispersion), or the fall (terrestrial attraction), are made at the same speed with a model or an object of real size. If we increase the duration by a slow motion, we increase at the same time the distance traveled by the object or its debris, giving the illusion of a larger object. The quality of a scene of displacement or destruction of a model was once again the budget devoted to this trick, the most accurate models and made of materials imitating to perfection those who constitute the real object, gave the best effect At the same time, the distance traveled by the object or its debris is increased, giving the illusion of a larger object. The quality of a scene of displacement or destruction of a model was once again the budget devoted to this trick, the most accurate models and made of materials imitating to perfection those who constitute the real object, gave the best effect At the same time, the distance traveled by the object or its debris is increased, giving the illusion of a larger object. The quality of a scene of displacement or destruction of a model was once again the budget devoted to this trick, the most accurate models and made of materials imitating to perfection those who constitute the real object, gave the best effect2 .

Idling is above all a process that is used extensively to create or emphasize a dreamlike or poetic effect. Thus, in 1928 , the Man with the camera , Soviet documentary realized by Dziga Vertov , although wanting to show only the reality, uses the device of the slow motion to make admire the aesthetic effort of various sportsmen, “a woman discobole, a hammer thrower, a pole vaulter, gymnasts, a volleyball team, a hurdles race, a trotting horse, an angel’s jump in the pool, a balloon coming right on the camera … Between each of these slow motion, the editing involves onlookers filmed close up and at normal speed 3 . ”

This poetry can also pour into the nightmare. In 1969 , the American director Sam Peckinpah uses for the first time in the cinema in a scene of violent action a slow motion that gives the effusions of hemoglobin and grimaces of pain victims an odious character. This is The Wild Horde , a film that challenged the Hays Code at the time , challenged by American filmmakers and audiences. In the Italian western It was once in the West , Sergio Leone evokes in flashback the trauma of the character of Harmonica ( Charles Bronson ) who”Seeing himself as a child, while Frank, by a sadistic game, perched on his shoulders his older brother, the rope around his neck. The time of the impossible mourning that seems to suspend the Harmonica gestures throughout the film is dilated in a slow motion where the young boy finally yields under the weight of his brother and collapses in the dust. Immediately after, the time of revenge comes Harmonica draws in a split second, ahead of Frank who then pays for his crime 3 . ” In 1970 , the French director Claude Sautet described a car crash seen inside the passenger compartment, in The Things of Life , where the character of Peter ( Michel Piccoli) is shown in the barrels his car makes, in the midst of objects that the spill disperses in the air (dust, pencils). An accident that is then re-shown at normal speed, seen from the outside; in a fraction of a second the life of a man swings, in a few seconds, he is plunged into a coma from which he will not go out. This use of slow motion is very common in today’s cinema, with all that digital effects allow ( Matrix , The Lord of the Rings ).

Slowing scientists

Cameras with high frame rate appear very early in the material reserved for entertainment cinema. Frame rates are multiplied by 3 or 4.

In 1925 , the French company André Debrie , which already manufactures a device popular with film circles around the world, the Parvo , develops and markets a camera, the Debrie GV, which takes up to 240 images per second. which at the time, projected at the standard speed of 16 frames per second, gives an idle of 15 times. This device is not intended for fiction films, its goal is to provide laboratories research machines, planes, cars, weapons, aerodynamics, etc., a way to observe how different materials are deformed in their movements. This camera is equipped with a classic intermittent mechanism with claws and counter-claws 4.

But other shots have been needed before to analyze extremely brief phenomena (explosions, shocks, breaks, crystallizations, arcs, etc.). At this speed, the intermittent filming of the film by claws is impossible. As early as 1904 , one of the assistants of Étienne-Jules Marey , the inventor of chronophotography (high-speed photography), the Briton Lucien Bull gets speeds of up to 4,000 images per second, with film driven in a continuous circular rotation (drum 1 meter in diameter rotating at 5,000 rpm ) per second and images of1 cm wide formed by a flashing light (magnesium electrodes), synchronized with the unfolding of the film in front of the lens, flashes causing flash formation of photograms . In 1930 , the rate reached 90,000 frames per second. In fact, the brevity of the shooting is that there are not 90 000 recorded images (but it is at this impressive rate that the photograms are recorded), there are at most a few hundred, but they make it possible to make an even shorter phenomenon perceptible. What is sought is what is called the strobe effect, improved, that is to say, the analysis of a phenomenon whose different phases can be observed as well in an illusory stopped image, as in motion, forwards or backwards. With the principle of light flashing, scientists are getting before the Second World War (before 1940 ), high-speed photographs, the shutter speed is 1 millionth of a second 5 .

Today, mainstream cameras can record at 1,000 or 2,000 images per second, and cameras at scientific destinations easily shoot at 3 or 6,000 frames per second. Examples of use are well known to the public, such as the crash tests of the automotive industry. As for the speed of shooting the fastest, it has been reached by the Massachusetts Institute of Technology in the United States for a few years , with 1 000 billionth of a second, which makes it possible to view the path of the photons of light. 6 , but the “film” itself, only lasts … 1 billionth second, a “film” that can only decipher scientists.

Bullet time

Main article: Bullet time .

The so-called ” bullet time photography  ” technique  (which could be translated as “ball speed”) is a direct adaptation of Eadweard Muybridge’s experience which corrected the knowledge that we still had in the 1870sgallop of a horse (and more generally a quadruped). Eadweard Muybridge had aligned 24 photographic chambers in front of which a rider was driving a horse at a gallop, whose chest dragged taut cords which triggered each successive passage of the apparatus. The 24 snapshots had shown that the four hooves of the horse leave the ground only once, when his legs gather under him before throwing him forward. This experience put an end to the pictorial representation of the horse which showed it in a spectacular phase of its gallop, the anterior and the posterior extended respectively in front and back, all above the ground as during a jump. A spectacular phase that does not exist. To prove it, it took the help of chronophotography.

The bullet time takes up this idea of ​​the alignment (linear or circular) of modern cameras capable of taking continuous photographs . No cords, the devices are triggered by a centralized computer system that has a picture taken successively by each device that resumes in its burst mode, as many photographs, all shifted very slightly in time and space. When we reproduce in a digital file each of the photographs – in chronological order – this results in a particularly surprising slow motion effect with a camera that seems to perform at the same time a tracking shot (lateral or circular).

The bullet time recalls that a film (it is Thomas Edison who, the first, adopted the English word film to designate his rolls of impressed film) is a succession of still images, of “animated photographic views” (as well as Louis Lumièredesignated his own bobineaux), an extension, therefore, of photography .

Slow sports

When sports competitions high-level, such as the World Cup of soccer , the tennis , the rugby , the Formula 1 , the MotoGP and the Olympics, a special recorder makes it possible to generate a continuous flow of signals at high speed, which allows instantaneous backtracking of the actions of interest or posing a problem of arbitration, which can thus be analyzed in slow motion, and this for each of the cameras of the device. This flow, big consumer of signals, is consequently virtual and ephemeral, its recording must have been ordered at the moment when the interesting or contestable action occurs. If the idle was not recorded at the time of its generation, it is definitely lost and the referee will be able to resort to a single passage image by image of the competition’s regular speed recording, to make a judgment on the action in question, recording less spectacular for the viewers but just as instructive for him.

Ultra slow motion in sports broadcasting

In May 2004, the invention of the  Superloupe by Aram Novoyan 7  is a turning point in the cutting of live sports programs. Major sports events are modified because cameras equipped with CMOS sensors   can now restore live slow motion up to 1000 frames instead of 25 or 75, which requires time to restitution The first live use of the Superloupe prototype took place during the Grand Prix de France of Formula 1 on TF1 in June 2004. Since the number of Ultramotion cameras on sports events continues to grow, the FIFA World Cup in 2006 had two cameras Superloupes while 6 years later the London Olympics in 2012 in use 34.

Nowadays (January 2018) these cameras are available in 4K UHD with recording speeds exceeding 1000 frames / second and are used in football refereeing aid (VAR) 8   voted by FIFA 9 in April 2017 However, it will be necessary to wait until January 10, 2018 for the match Amiens-PSG 10   in cup of the French League for the Ultramotion camera Superloupe to be included in the aid system for referees

Related Articles

  • XT3 Server and Multicam [LSM] .
  • chronophotographie
  • Bullet time

References

  1. ↑ Marie-France Briselance and Jean-Claude Morin, “film grammar”, Paris, New World Publishing, 2010, ( ISBN  978-2-84736-458-3 ) , 588 pages, quote from page 27
  2. ↑ Marie-France Briselance and Jean-Claude Morin, “film grammar”, op. cited, pages 375 to 379
  3. ↑ a and b ditto
  4. ↑ http://cinematographes.free.fr/debrie-grande-vitesse.html  [ archive ]
  5. ↑ Lo Duca, “Film Technology”, Paris, Presses Universitaires de France, 1943, pages 99 to 102
  6. ↑ timereel.nouvelobs.com
  7. ↑ ( in ) ”  Aram Novoyan Inventions, Patents and Patent Applications – Justia Patents Search  ”  [ archive ] , on patents.justia.com (accessed January 11, 2018 )
  8. ↑ ( en ) ”  Video assistant referee  “ , Wikipedia , ( read online )
  9. ↑ ”  International Federation of Football Association  “, Wikipedia , ( read online )
  10. ↑ ”  Video support set up for Amiens / PSG  “, CulturePSG , {{Article}}  : ” année ” or ”  date ” missing parameter  ( read online  [ archive ] )

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