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The art of cinematography is, above all, the art of lighting, and the British term for the chief of the camera crew, lighting cameraman, comes closer to the matter than the Hollywood director of photography. In motion-picture photography, decisions about exposure are governed by the overall style of film, and light levels are set to expose the particular film stock at the desired f-stop.
Light sources
The earliest effective motion-picture lighting source was natural daylight, which meant that films at first had to be photographed outdoors, on open-roof stages, or in glass-enclosed studios. After 1903, artificial light was introduced in the form of mercury vapor tubes that produced a rather flat lighting. Ordinary tungsten (incandescent) lamps could not be used because the light rays they produced came predominantly from the red end of the spectrum, to which the orthochromatic film of the era was relatively insensitive. After about 1912, white flame carbon arc instruments, such as the Klieg light (made by Kliegl Brothers and used for stage shows) were adapted for motion pictures. After the industry converted to sound in 1927, however, the sputtering created by carbon arcs caused them to be replaced by incandescent lighting. Fresnel-lens spotlights then became the standard. Fresnel lenses concentrate the light beam somewhat and prevent excessive light loss around the sides. They can also, when suitably focused, give a relatively sharp beam. In the studio there are racks above and stands on the floor on which lamps can be mounted so that they direct the light where it is wanted. The advent of Technicolor led to a partial reversion to the carbon arc because incandescent light affected the colors recorded on the film. Around 1950, however, economic pressures caused Technicolor film to be rebalanced for incandescent light.
The modern era in lighting began in the late 1960s when tungsten-halogen lamps with quartz envelopes came into wide use. The halogen compound is included inside the envelope, and its purpose is to combine with the tungsten evaporated from the hot filament. This forms a compound that is electrically attracted back to the tungsten filament. It thus prevents the evaporated tungsten from condensing on the envelope and darkening it, an effect that reduces the light output of ordinary gas-filled tungsten lamps. The return of the tungsten to the filament means that the incandescent lamp can be run with a long life at a higher filament temperature and, more important, remain at precisely the same color temperature. These lamps are now sometimes provided with a special multilayered filter to give a bluish light that approaches the color of daylight. Halogen lamps give brilliant light from a compact unit and are particularly well-suited to location filming.
The principal light on a scene is called the key light. The position of the key light has often been conventionalized (e.g., aimed at the actors at an angle 45 degrees off the camera-to-subject axis). Another school of cinematographers prefers source lighting, in the tradition of Renaissance and Old Master paintings; that is, a window or lamp in the scene governs the angle and intensity of light. A fill light is used to provide detail in the shadow areas created by the key light. The difference in lighting level between the key plus the fill light versus the fill light alone yields the lighting contrast ratio. The “latitude” of the film, or the spread between the greatest and least exposure that will produce an acceptable image, governs the lighting contrast ratio. For many years, the latitude of color films was so restricted that it was thought necessary to have numerically low lighting ratios, typically 2 to 1 (a very flat lighting) and never more than 3 to 1. The introduction of Eastman 5254 color negative in 1968 and the even more sophisticated 5247 in 1974 opened a new era in which color film was exposed with higher ratios approaching the previous subtleties of black-and-white.
Light measurement
Precise control of exposure throughout filming is necessary to maintain consistent tones from shot to shot and to give an overall tenor of lighting that suits the pictorial style. To determine light levels in the studio and on interior locations, an incident light meter is primarily used. This type of meter is recognizable by a white plastic dome that collects light in a 180-degree pattern (the dome is an approximation of the shape of the human face). Because it measures the overall light (calibrated in footcandles) falling on the scene, it may be used without the actors present.
Reflected light readings measure the average light coming toward the camera from the scene being photographed. This works well for average subjects but gives wrong exposures if the background contains either many bright areas, as in a beach scene, or very dark areas, as in front of a dark building. In such cases the photocell must be held not at the camera but very close to the subject of interest, to eliminate the effect of the background. This is also the case when the scene contains a good deal of backlight. These shortcomings eventually led to the development of the spot meter.
Spot measurement readings measure the light coming toward the camera from selected spots in the subject being photographed. The meter for this purpose has an optical system that covers measurement of a spot of about one degree, making it extremely useful on exterior locations.
Light is also measurable in terms of color temperature. Light rich in red rays has a low reading in kelvins. Ordinary household light bulbs produce light of about 2,800 kelvins, while daylight, which is rich in rays from the blue end of the spectrum, may have readings from 5,000 to more than 20,000 K. The color temperature meter uses a rotating filter to indicate a bias toward either red or blue; when red and blue rays are in balance, the needle does not move. Some meters also use red/blue and blue/green filters for fuller measurement.
The general practice has been to shoot the entire picture on stock balanced for artificial light at 3,200 K. Lights for filmmaking generally range between 3,200 K and 3,400 K. For daylight shooting, an orange filter is employed to counter the film’s sensitivity to blue light. Although color-correcting filters are produced in a great many gradations, the No. 85 filter is generally used to shoot tungsten-balanced color film outdoors. For mixed-light situations where daylight enters through windows but tungsten light is used for the interior, the practice has been to cover the windows with sheets of plastic similar in color to the No. 85 filter. This reduces the color temperature of the natural light to that of the artificial light. When the windows are very large, blue filters are sometimes placed on the lights and the No. 85 orange filter is used on the lens, as if filming in exterior daylight. Yet another approach is to supplement natural daylight with metal halide (daylight-balanced) lights. With the increase in location shooting, daylight-balanced high-speed films have been introduced to allow shooting in mixed-light situations without light loss due to filters.
Film processing and printing
In the early days of motion pictures, films were processed by winding on flat racks and then dipping in tanks of solution. As films became longer, such methods proved to be too cumbersome. It was recognized that the processing system should have the following characteristics: it must run continuously; it must be lighttight and yet capable of being loaded in daylight; and it must be as compact as possible to provide a minimum air surface for the processing solutions. A general form evolved that is still in use.
For continuous operation the film must be passed continuously through the solutions and folded back over rollers that do not touch the emulsion surface. It must be handled very carefully, as the impregnation with solution weakens the support, and the sprocket holes should not be engaged. Drive should, therefore, be accomplished by a light friction force at the edges.
Splicing on a fresh film without affecting the motion of the part of the film being processed is handled by using a storage unit or reservoir. This reservoir has a variable capacity so that the output end can be giving out film while the input end is stationary as the new film is spliced. Lighttight gates prevent all but a short length of film being light-struck at the very beginning or end of the film (and leaders may be used). The take-up-reel case is fastened in a lighttight way to the storage unit so that after splicing, the film is unreeled into the storage and processing units until the other end is reached, ready for splicing to the next film after changing cases.
Many tank shapes have been tried. Long vertical tanks provide for several passes of the film through each tank. The spools are designed so as to hold the film at the edges by friction. There are a number of types of drive, but all function gently to avoid strain. Sometimes the spools have multistepped edges to accommodate various film widths. The lower spools (or “diabolos”) are more or less free but guided in a loose fashion so that they will not jam or tangle. The long vertical tanks give a minimum of air surface to the solution. The motion of the film through the liquid can be sufficient for proper contact of the film with the solutions, but sometimes submerged sprays with small jets of fine nitrogen bubbles are provided to increase the agitation.
The last receptacle in the processing sequence is a drying oven. There are several designs, some of which generally resemble the tank but without solution and are provided with heating elements. This receptacle does not need to be lighttight.
The processing steps for the many different types of film are similar in principle, though there are variations in specific solutions and treatments. One variation is known as reversal processing. After partial development, the camera original is bleached and given a second exposure of uniform white light. This yields a positive rather than a negative image and thus saves the cost of an additional generation.
In laboratory parlance, the major functions are divided into “front end” and “release print” work and may be performed at different facilities. Front end work begins even before shooting with tests by the cinematographer on the same film stocks that will be used for the production. These will be used as a guide when takes from the camera negative that come in from each day’s shooting are printed. A color video analyzer reads the red, blue, and green records of the tests over a range of six f-stops to establish “printer lights.” As desired, the work print may be “one light” (given uniform exposure) or “timed” (exposure corrected for scene-to-scene variations).
The original negative is stored until postproduction is finished. Positive work print is furnished in 1,000-foot rolls for editing. When all editing, including the insertion of optical effects and titles, is completed, the negative cutter matches the original camera film frame by frame at each editing point. The edited camera negative is combined with the synchronized sound track negative into a composite print called the answer print. (The first answer print is rarely the same as the final release print.) After all color-correction and timing takes place, the information is recorded on perforated paper tape that serves to control both the exposure for each shot and the louvered filters that add red, green, and blue values.
For theatrical distribution, exhibition release prints are not normally struck from the original camera negative. The original negative is used to make a master positive, sometimes known as the protection positive, from which a printing negative is then made to run off the release prints. Alternatively, a “dupe” negative can be made by copying the original camera negative through the reversal process. This yields a color reversal intermediate (CRI) from which prints can be struck.
Printing takes a number of different forms. In contact printing, the master film (or negative) is pressed against the raw stock; this combination is exposed to light on the master film side. In optical printing, the master film is projected through a lens to expose the raw stock. In continuous printing, the master film and the raw stock both run continuously. Continuous printing is usually contact printing but can be optical, through a projected slit. In intermittent, or step-by-step, printing, each frame of the master film is exposed as a whole to a corresponding frame space on the raw film.
It is possible to print from one size master film to another size raw stock, such as 35-mm to 16-mm, or vice versa. In such cases the printing must, of course, be optical, and in the examples cited must be intermittent if there is a sound track. This is because 35-mm sound film has a spacing between frames and 16-mm does not. The sound track must be printed separately. The preferred method for making 16-mm versions of 35-mm films is to make a 16-mm negative by reduction from the 35-mm negative. Sometimes a 35-mm release print is reduced and printed by reversal, but this yields a coarser image. When 16-mm film is “blown up,” the 16-mm negative is immersed in a solution that conceals scratches and grain as it is being rephotographed; this process is called wet-gate printing.
Film prints to be used for projection are given a coat of wax over the sprocket-hole areas. This eases the film passage between the pressure plates at the projection aperture.
