Accelerated shooting - Rapid. Cine or video with a frequency of 32 to 200 frames per second. Professional video shooting

Accelerated (rapid) filming, at a frequency exceeding the standard (24 fps), is used to create the effect of slow motion, which is in demand in the projection of films, television, computer games, scientific cinematography. It is used to capture sports events, to reproduce the movement of layout elements or natural phenomena according to the established time scale. The screen demonstrates an imaginary slowing of the pace of the phenomena that were shot, and the viewer is given an opportunity to view the intermediate phases of the processes and the poorly discernible details.

Features of accelerated shooting

Types of shooting:

• Accelerated, or rapid shooting (32-200 fps) is carried out by means of standard equipment with a clamshell mechanism and intermittent motion of the film;
• More rapid shooting with a frequency of 200-10 000 fps is ensured by continuous uniform movement of the film with the use of optical and electronic methods of light manipulation. Accelerated shooting is conducted from the hands of a moving vehicle using professional or conventional amateur equipment with an extended frequency range necessary for image stability.

The technology of filming has remained almost unchanged since 1955, except for the creation of an electronic shutter, although the image is currently fixed not on the film, but on a sequence of digital matrices, thanks to which the frame rate is 100 million per second.

The degree of acceleration is limited by the capabilities of the camera, its design and dynamics. For amateur equipment is characterized by accelerated shooting - 64-72 fps, for the professional - 360-600 fps. Modern cameras are able to provide a frequency of 200 fps with its gradual increase in order to obtain a special speed increase effect. If more acceleration is required, then they resort to manipulation of the cadres on the film.

Frame frequency

There are a variety of types of filming in scientific and applied cinematography, in particular for the study of fast flowing phenomena and processes. One of them is high-speed, or rapid shooting, with a frequency of more than 250 frames per second, allowing you to capture processes that are inaccessible to the perception of the human eye due to short-term or high-speed phenomena.

The number of research objects can include:

• Movement of living beings: frame rate is from 100 to 300 fps, exposure - 1/1000;
• Functioning of mechanisms (1-10000 fps);
• Destruction and explosions (10-100 thousand fps);
• Shock waves of gases (100 thousand - 1 million k / s);
• Electric discharges (10-100 million fps), and the like.

Technique

Due to a variety of conditions, a wide range of technical facilities and a variety of frequencies, professional video shooting of high quality objects is possible. High-tech equipment, in addition to standard image processing mechanisms, also uses optical accelerators, high-speed gates, electronic and optical converters.

High-speed photography is usually carried out by means of pulsed light sources (gas-discharge lamps, explosive light sources, spark gaps with an air gap).

Chronophotography is an intermediate way between photo and filming to capture successive phases of phenomena using a rotating slit shutter. The resulting images are layered on each other and combined into a single tape. The method is used for the continuous movement of the object of observation. Unique effects are provided by an open lens with pulsed lighting.

Methods of high-speed cinematography

1. Imprinting on intermittently moving film is carried out at a frequency of 600 fps with the use of a mechanical film transport system.
2. More accelerated shooting at a frequency of 1000 fps is realized with the use of pneumatic devices or with the mobility of the film due to the elasticity of the loops that are formed behind the channels of the film.
3. To achieve higher frequencies, moving photosensitive materials are used.

The effect of sharp pictures of successive transformations is possible when the film is displaced relative to the object in the following ways.

Electronic commutation

The method in which slotted obturators cut off the limited time points for exposing the frame. For the shortest period of time, the frame shift relative to the optical image does not exceed the permissible blur of the negative. It will require intermittent illumination with pulsed flashes (duration 10-7 fractions of a second) or a shutter similar to the shutter located in front of the frame connector, but instead of a cutout there may be a miniature slit (one or several).

Optical switching

If accelerated imaging involves a still image relative to the uniform motion of a film, it is necessary to neutralize the displacement of the light-sensitive material relative to the image in the exposure interval of the frame by moving the light-reflecting optical system operating at a speed and in the direction of film movement.

To realize the optical compensation, a mirror polyhedron, a glass plate or a prism in motion are suitable. The size and position of the optical element must ensure that the linear displacement corresponds to the motion of the frames. The film should be placed on the surface of the polyhedron in a special channel of the film. The method is used for small-scale processes.

The limit of increasing the frequency during electrical commutation is limited by the possibility of reducing the interval between flashes, and with optical speed, the speed of rotation of the shutter disk and its diameter.

Slowing the projection

For visual viewing, slow motion is used on the screen, which is possible both with increasing the frequency of filming and slowing the motion of film in the projector. The disadvantage of the method is visible discontinuity, and some high-speed processes generally fall out of sight, hiding between the captured frames during the survey. If the deceleration is more than 1 fps, the demonstration of the image resembles a slide show. Therefore, an optional slowdown is often replaced by an accelerated survey.

Modern methods of filming

1. Modern cameras are equipped with an electronic stabilization system, but still high-quality accelerated shooting is created using an adjustable length support, a "monopod" to ensure image stability without jitter.
2. Vertical objects and sides of the frame should be parallel.
3. Such methods of video shooting, like the alternation of close-ups with small and medium, are considered a good style. Overuse of the scaling system tires the viewer, so it's better to stop the recording sometimes, take the picture to the desired scale, and then continue.
4. The most optimal duration for perception is a plot of about 5 seconds, a maximum of 12 to preserve the lively and dynamic nature of the footage.
5. Setting the white balance in an artificially lit room is recommended to be done manually.
6. The horizon line is not the last characteristic, which is distinguished by professional video shooting: it should pass at the level of the middle line of the viewfinder or a little higher. Scenes in which the upper part of the frame is occupied by the celestial space by 2/3 are perceived with stress.
7. To make the medium and large-scale frames medium, you can place an object in front of the lens, unobtrusively creating an idea of the depth and scale of the image.
8. When choosing the camera angle, different perspectives should be considered, going beyond the stereotypes, for example, to show the object from the viewers and "judges" side, as well as from the eyes of an outside observer. And each such step for the operator is a new turn in his skill and a new discovery that raises his level.

It should also be mentioned professional ethics: during large events there are not so many profitable positions that are suitable for successful shooting, so it is worth taking care of all the necessary conditions in advance.