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.