ABSTRACT
A key element of many graphic projects is a photographic image captured with a conventional optical camera. Light reflected from the object or scene passes through the camera's aperture and lens system and impinges on the
surface of the light-sensitive film placed in the camera's focal plane. Colour film has three layers of emulsion on a cellulose acetate base. Each of the three layers is sensitive to only one of the primary colours red, green or blue. The emulsions are thin, gelatinous coatings containing light-sensitive silver halide crystals in suspension. When exposed to light, each emulsion reacts chemically, recording areas where its particular colour appears in the scene and forming a latent image on the film. When the film is developed, particles of metallic silver form in areas which were exposed to light and each emulsion releases a dye which is the complementary colour of the lfght recorded - blue light releases yellow dye, green light releases magenta dye and red light releases cyan dye. Complementary colours are used because they reproduce the original colour of the scene when the film negative is processed to produce the final colour print or transparency. Because the sizes of the silver halide particles in the film emulsion and the silver particles formed during the development process are very small, the resolution of detail in the final image is very high. To the unaided eye, the image appears to have continuous tone, with colours blending smoothly from one to another. Only when the image is considerably enlarged does the 'graininess' of the particles become visible.
