Cinematography

I

Introduction

Cinematography, art of making motion-picture films. Although Thomas Edison had patented the kinetoscope in 1891, incorporating many of the important features of the modern cine-camera, it was the launch in 1895 by the Lumière brothers in Paris of the Cinématographe, projecting films onto a screen for a large audience, that introduced the new mass art form of the cinema. It only needed the invention of practical, synchronous sound systems—Vitaphone in 1926 and Movietone in 1931—for the foundations of modern cinema to be complete (see Cinema, Early Development of).

The functioning of the cinema depends on two properties of the human eye and brain. The first is referred to as persistence of vision. If an image of a static light is focused onto the retina and is switched on and off slowly, we can see the flashing. If the frequency of flashing is increased there will come a point where the light appears to be steady. This is known as the critical fusion frequency. When the ambient lighting is at a low level and the retina is said to be dark adapted, this frequency is lowered.

A further effect of this phenomenon is that if the image of a continuous light moves on the retina, the persistence of the nerve impulses can cause a smearing of the image, which is most marked when the system is dark adapted. This is why a torch rotated in a circle in a darkened room appears to the eye as a continuous circle, since the source of light keeps returning repeatedly to the same position, before the retinal activity has appreciably faded.

Another property of the system of visual perception is referred to as apparent motion. If separate lights are switched alternately, at the correct frequency and spacing, we seem to perceive a light moving between the two positions. This property of brain neural networks is sometimes known as the phi phenomenon. It is probable that it also plays an important part in the illusion of smooth motion in the cinema, but cannot fully account for the illusion in static scenes.

Cinemas are darkened so that viewers' eyes are dark adapted and the critical fusion frequency lowered. In addition, the projector has multiple blades, so that each image is projected twice. This reduces the length of the dark part of the cycle and improves the subjective continuity. The rapid succession of still images (usually 24 per second) produces the impression of a continuous image, and movement seems to be smooth, even though actually presented in steps. The effect is further enhanced by the blurring of moving objects, caused by the relatively long exposures in a cine-camera, usually about of a second, only static or very slow-moving images being sharply “frozen”.

For reasons discussed below, most productions are still shot on film. The first large-scale cinema films to be shot using digital cameras have been released and digital technology is likely to take over from much of the present use of film cameras and cinema projectors eventually.

II

The Cine-Camera

Although the fundamental purpose of a cine-camera, the taking of still photographs, is basically similar to that of other cameras (see Photographic Techniques), the need to take so many photographs per second means that the necessity for rapid transport of film through the camera dominates the design of the mechanism. Since, at 24 frames per second, one minute of filming uses over 27 m (90 ft) of 35-mm film, cameras are fitted with magazines that can hold 122 m (400 ft) or 305 m (1,000 ft) of film. In order to draw the film smoothly off such large rolls, and in order to wind it up again after exposure, the film has to run continuously in the camera. However, to take the photographs, the film must move in steps where the individual frames are exposed.

Continuous drive of the film is provided by one or more toothed drums or sprockets round which the film passes, held in contact with the teeth by guide rollers. The sprocket teeth engage in perforations along one or both edges of the film and drive the film smoothly.

The gate is a metal plate, with a rectangular gate aperture, against which the film is held flat, from behind, by the spring-loaded gate pressure pad. In front of the gate is the lens, which focuses inverted images of the subject being photographed onto the surface of the film, through the gate aperture, to form the frames on the film. In cine-cameras, the film usually runs vertically downwards and the height of each frame, plus the space between it and the next frame, is usually the length of four perforations, whereas, in a still camera, where the film lies horizontally, each frame takes up the length of eight perforations.

Between the lens and the film is a continuously rotating shutter, which alternately opens to expose the film in the gate and then closes while a fresh section of film is pulled down into the aperture. A typical shutter consists of a blade that is semicircular, so that the angle of the open section is 180°. The shutter is, therefore, open for half of the time and closed for half of the time. At 24 frames per second, this produces an exposure of of a second. On some cameras the exposure can be varied by altering the shutter angle.

The intermittent movement of the film through the gate is usually achieved by a claw mechanism that moves in a continuous cycle, engaging with the perforations, pulling the film downwards in a step, and then retracting to recover during the exposure. It then repeats the action. In order to guarantee that the film is accurately located and absolutely still during exposure, many cameras are fitted with register pins, which slide into the perforations and secure the film during the exposure and then retract for pull-down. In order to reconcile the continuous and intermittent drive of the film, the camera is loaded with small, free-standing loops of film above and below the gate.

To achieve accurate framing, most cameras have reflex viewfinders. The front surface of the shutter is set at 45° to the axis of the camera and is mirrored so that, during periods when the shutter is closed, the image is reflected at right angles onto a ground-glass screen, or fibre-optic screen, exactly the same dimensions as the frame of film in the gate. The camera operator has a magnifying viewer, through which he or she can view the image on the ground-glass screen, from the back of the screen. Many film cameras also have a miniature video camera that transmits the image on the ground-glass screen to a closed-circuit television system for monitoring and playback. This is referred to as a video assist.

The quality of the projected image depends on the area of each frame. For professional film-making, film 35 mm wide is the norm, although 16-mm film is widely used for television and documentary film-making. Frequently, a version of 16 mm, called Super 16, is used, where only one set of perforations is employed for film transport, freeing up extra space on the film. The aspect ratio of the resulting image can be used for television presentation, with part of the top and bottom of the frame masked in black. It is also well suited for showing on wide-screen televisions and high definition television systems. In addition the image can be enlarged to 35-mm wide-screen for theatrical distribution. Amateur use of 8-mm film has largely been replaced by the use of video camcorders. In some selected cinemas, enlargements of the image onto 70-mm film can be used, to produce the best quality of presentation.

III

Digital Cinematography

Being entirely electronic, digital cameras have no moving parts. The various intensities of the image produced by the lens are focused onto a solid state chip called a charge-coupled device (CCD). The typical CCD has a much smaller area than a frame of film, being ’ of an inch (16.93 mm), but comprises over two million elements or pixels, laid out in a pattern 1,080 pixels high by 1,920 pixels wide. This ratio is called common image format (CIF). The intensity of light on each cell of the array is converted to 12-bit digital information for storage on high capacity memory. To record colour, the camera has a beam-splitting device that splits the picture into three identical images. The images are then passed through a primary colour separation filter (red, blue, and green respectively) to separate the relative intensities of each colour and the colours are recorded by three separate CCDs.

The data stream from a digital camera is recorded on a digital tape recorder. A lower resolution video version is later made for editing. (See Digital Editing, below.)

IV

Laboratory Processing

The very large footages of film produced by cine-cameras are processed on big, continuous-processing machines, which develop the negative images on the film. These are then printed onto positive film on a printing machine. Most printing is done using continuous contact machines, where the developed negative and unexposed print films are run together, in contact, past a controllable source of light. The light passes through the negative, exposing the images directly onto the print film, which is then developed to produce the positive images. Other printing machines consist of a projector that uses a lens to project the negative image directly onto print film in the gate of a special type of camera. This type of step optical printer can be used for a wide variety of purposes such as enlarging (“blowing up”) from a 16-mm negative to a 35-mm print and for many special effects.

The light used for printing is produced by a special additive source, where the amounts of red, green, and blue light can be regulated independently to control both the exposure and the colour balance of the individual shots. By correcting small variations between shots, smooth photographic continuity is achieved. The technique of controlling the printer light settings is referred to as grading or timing the print.

Traditionally, the practice was for the first print to be sent back to the film-makers as soon as possible, usually the following day, so that they could check that the scenes had been filmed correctly. These prints are called rushes or dailies and, after viewing, were used by the editor to assemble the shots into the cutting copy or work print. They were joined or spliced in the right order and the right points at which to cut between the shots were determined. Recently, digital techniques have involved the editing decisions being made using virtual cutting copies in a computer. However, in fully budgeted films the first print is still made, as most film-makers wish to see their rushes on film to enable them to make accurate judgements about the photographic quality of the material as it will be seen on release in the cinema. If necessary, scenes may then be re-shot. If cost savings are critical, video versions of the rushes may have to be accepted as dailies, though high-quality telecine and video projection are necessary if the judgements are to be relied upon.