Lighting Units.

Lighting Units

Introduction

On feature films, lighting is exceptionally important. It is usually the Director of Photography’s responsibility to make sure that the lighting design is perfect, not only the camera positions and how the scene will be shot. The lighting affects the dramatic intensity of the scene, and has a very powerful effect. In this essay I will be discussing the different types of lighting units, focusing mainly on interior lighting units. I will mention different types of bulbs, as well as explain briefly what Colour Temperature is. I will also show what the different kinds of lights are used for.

Lighting Units

Lighting units are what we refer to as bulbs, lambs or globes. They are identified by type and power consumption, for example a 5K spot is a 5000-watt (5-kilowatt) spotlight. The lights are usually balanced for Tungsten (3200°K). The brightness of a bulb is indicated by its wattage.

The term “falloff” refers to the rate of change from light to shadow. The rule for typical open bulbs is that the falloff in intensity is inversely proportional to the square of the distance, thus, moving an object twice as far from a lamp results in it being lit by ¼ the amount of light. This means that falloff will be exceptionally sharp the nearer you are to the light source, therefore soft light sources will have a sharper falloff than focused, hard light sources.

Bulbs

There are many different types of bulbs, and they differ in the type and colour of light that they emit. Household bulbs can be used with video, as long as the DP is able to maintain a good white balance. Because the colour temperature is only about 2900°K, they produce a yellow-orange light instead of white on tungsten-balanced colour film. They are mainly used in practical fixtures, such as a side or table lamp in a scene.

Photo bulbs can be either photofloods or reflector floods. A photoflood is a lamp used by photographers, which gives a bright white light. Because they have a thin filament, they give a good flash effect (e.g. lightning). They have a relatively short life, however, so they should not be left on for any length of time.

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Tungsten-halogen bulbs employ a tungsten filament surround by halogen gas encased in a quartz crystal bulb. During the lamp’s life, tungsten evaporates from the filament, and would normally deposit itself on the glass wall of a tungsten lamp. This would make it blacken; causing the output of the lamp to reduce until it finally blew. In a tungsten halogen lamp, the tungsten combines with the halogen gas elements present in the lamp envelope and is re-deposited back onto the filament. This process needs a very high temperature to operate, so tungsten halogen lamps are able to be a lot smaller, and run a lot hotter, than their tungsten equivalents.

An HMI (Halogen-Metal-Iodide) bulb is a mercury-halide discharge lamp with a colour temperature of 5600°K or 6000°K (daylight balance illumination). They are much more effective than tungsten, and produce up 4 times more light. They are obviously much more expensive, but a major advantage is that they give off less heat than tungsten. Depending on the country’s power source, HMI can only be used at certain frame rates otherwise they will flicker. They are operated using AC power, and require a heavy ballast unit to control the electric current going to the lamp.

Fluorescent lighting falls into two categories: standard fluorescent fixtures (typically found in office and institutional settings) and specially designed fluorescent lighting units for film and video work. Fluorescent bulbs are blue-green in colour, and need to be balanced by either placing a Negative Green Gel on the light, or else placing a Positive Green Gel on tungsten so that the fluorescence can be balanced. Just like HMI bulbs, fluorescent bulbs suffer from a flicker problem, which becomes evident when shooting at a shutter speed higher than one sixtieth of a second.

Colour Temperature

Colour Temperature is a measure of the warmth or coolness of light sources and colours. It is measured in degrees Kelvin. The human brain automatically compensates for different colour temperatures, however a film or video camera can’t. This means that what we see as white may appear to have a blue, orange or green hue when no colour correction or white balancing is used for video. Daylight is approximately 5600K and Tungsten Halogen is approximately 3200K.

Colours can be balanced by using a colour filter or gel. This is a sheet of plastic usually composed of a coloured resin sandwiched between two clear pieces. The coloured filter absorbs all the colours of light except the colour of the filter itself, which it allows through. For this reason, denser colours get very hot, and can burn out very quickly.

Types of Lighting Instruments

There are four basic types of lights that are used in film and television, namely the spot, the broad, the flood, and the soft light. A spotlight has a narrow beam that casts well-defined shadows. The broad is a rectangular shaped light that has a wider beam, casting softer shadows. The floodlight throws a very broad, even illumination in a circular pattern that casts diffused shadows. Soft lights are used for general illumination, creating shadows that are barely noticeable. They are used as a fill light in TV studios to eliminate shadows and balance the key light.

Most lamps are fitted with “barn doors”, which are black metal flaps fastened to the front of the lamp housing. These flaps are used to keep light from falling where it’s not wanted. Use of barn doors is most important on backlights, which can cause objectionable lens flare if their light is allowed to strike the camera lens directly.

Sometimes scrims are used to soften lights or reduce their intensity slightly. They are either coarse gauze, or a fine metal mesh used to reduce the intensity of light from globes without affecting colour temperature.

3-Point Lighting

The standard photographic lighting technique is known as the “photographic principle” (Zettl, p. 33). This refers to the triangular arrangement of the key light, the back light, and the fill light. The key and fill lights are on opposite sides of the camera (at a 45° angle), and the back light is directly opposite the camera.

The key light is the principle source of illumination, revealing the basic shape of the object or event. The back light separates the figure from the background, and provides interest. The fill light controls the falloff.

Conclusion

This essay listed some of the major lighting units used in television and film production. I discussed the types of lighting instruments and how 3-point lighting works. I explained the different types of bulbs available, and what Colour Temperature is. As we can see, lighting is a complex procedure and involves careful preparation and planning in order to create the desired dramatic effect.