We've all seen the moment when the heroine emerges from the gloomy mansion into the daylight, symbolizing the beginning of her new life. We've also seen the warm glow of a couple having a romantic dinner, and the menacing face of a vampire appearing from the shadows. Lighting is necessary to expose film — to alter the emulsion and create an image — but with a little bit of care, it also creates a mood.

The Upshot of Lighting

Proper lighting is a balance between exposure, sensitivity, and contrast. A quick way to determine this is the use of a pan glass. Looking through this small, hand-held lens shows the scene you're filming at a higher contrast, effectively mimicking how the image will look on film. Your cinematographer can then make adjustments before shooting.

The intensity of light being given off by a particular source is measured in foot candles (fc), which is the amount of light received from a standard candle one foot away. In metric terms, the distance is thirty centimeters and is called lux. Since we rarely look directly at a light source, most of the light we see has been reflected off all of the objects around us. The reflectivity of a surface or surfaces determines the foot candles that make up the high and low range of your shot.

Knowing the Surface

A smooth surface is said to be specular because it reflects the light more directly. A rough surface, such as fabric, absorbs much of the light, and the specularity is more diffuse, reflecting smoothly in all directions. It's crucial for various departments, such as set dressing and wardrobe, to work closely with the camera crew well in advance to determine if there will be problems with reflections during filming.

The Setup

The major components of setting up the lighting for any shot come down to three broad categories: key light, fill light, and back light. The key light is the primary source. It should mimic the motivating light in both intensity and direction. For instance, if there's a large window in a room, the key light may simulate sunlight coming through that window.

Fill light refers to a nondirectional, softer light, often placed in a position opposite the key light in relation to the camera. Its job is to “fill” the shadows caused by the key light, softening the subject to more realistic ambience. The back light, as you might guess, is one placed behind the subject, aimed toward the front. While this will create shadows on the front of the subject, it will also generate a sense of depth and emphasis.

The secondary thing to consider when lighting a scene is color. Since color is by definition light, white light is made up of equal parts of red, green, and blue (RGB). These colors can be separated out by use of colored bulbs or by putting a colored transparency between the light source and the subject. This can be important, not only for matching or imitating a particular motivating light, but to communicate mood or even ambient temperature.

Available Versus Practical

Whether you choose to utilize the available light of a location or the practical light provided by household lamps and streetlights, odds are you'll end up using professional lighting equipment to enhance or simulate the real thing. In this regard, there are several considerations, including housings, reflectors, and bulbs.

The Basic Housing

The structure of the lighting instrument is called a light housing. Open-face housings are simply a bulb in front of a reflector. These are lightweight and provide an even spread of light. The bulb of the Fresnel light is behind a lens that amplifies and focuses the beam. The housings are larger and heavier than open-face units, but provide a better quality of illumination. The light from the parabolic aluminized reflector (PAR) is comparable to the headlight of a car. Because the bulb, parabolic reflector, and lens are all fixed in the housing, the beam cannot be altered.

Reflections

While reflections on your set may be bad, reflectors in your lighting unit are crucial. Often shaped for a specific purpose, they bounce the light out of the housing in a particular direction and manner depending on their shape. Common shapes and their uses are as follows:

• Parabolic reflectors surround the bulb, creating a highly directional, highly intense beam.

• Flat or curved reflectors in a broad light are usually dimpled, and produce a more diffuse beam.

• Bounce light is not a reflector in a housing, but rather a method of pointing a light at something on the set and allowing the light to “bounce” back onto the subject. The reflecting surface can be an object made for this purpose, or simply the wall or ceiling of the room itself.

Bounce light provides a quick and effective way to light a room evenly and softly. As such, it's often ideal for documentary-style filming.

Getting Radiant

At the center of every lighting unit is the bulb. A far cry from a sixty-watt reading lamp or even the huge bulbs of previous generations, modern bulbs are smaller, cooler, and more lightweight. It's important that you understand the types of bulb and their functions. These bulbs include:

• Tungsten lights, which are very big and bright. Usually used as floodlights, they have a very limited life span, especially in terms of brightness and color stability.

• Quartz-halogen lights, which are tungsten-based but do much better at maintaining a consistent amount of light and color balance.

• Carbon arc lights, which create a spark between two carbon electrodes to create a light strong enough to match daylight. The units themselves are big and heavy, and the electrodes must be trimmed and replaced about every thirty minutes.

Hydrargyrum medium-arc iodide, or HMI, is a mercury-halide arc lamp. HMIs are the new solution to many of the old problems. The mercury-arc discharge lamps are only at full power for a fraction of every second, keeping them cooler while making them more efficient than quartz lights. One difficulty is the large, heavy ballast that accompanies each unit. Another big drawback is the price. It would be cheaper to buy an entire quartz-halogen light head than to replace a single HMI bulb.

Be sure that everyone working on your film is extremely careful when dealing with very high voltages and extremely hot lights. Never think that lighting a set is as simple as flicking a switch. Be sure your gaffer has had sufficient training, and that your power requirements don't exceed the limits of your shooting facility.