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Measuring Light
It used to be that cinematographers always had a light meter in hand. But for digital video, handheld light meters are used with diminishing frequency. Instead, digital video cameras offer built-in tools that can help you determine the best lighting for a scene:
nZebra stripes in the viewfinder help you identify which parts of an image are overexposed.
nIn-camera light meters help you adjust the f-stop to get proper exposure. Some cinematographers choose an f-stop and then set all the lighting to expose correctly at that f-stop.
nHistogram displays show you the range of lights and darks in an image.
Be aware that not all cameras offer all of these tools. We discuss using these camera features in detail in Chapter 7.
Make a Lighting Plot
Obviously, lighting is a very hands-on stage of production. However, there’s still plenty of planning that you can do to make sure you have the gear you need and to make the best use of your time on the set. Once you’ve chosen your locations, you should meet with your lighting crew or director of photography and try to plan exactly what type of lights you’ll want and where. Try to rough out some floor plan sketches and determine where you’ll need each piece of equipment. This is also a good time to assess how much power you’ll need, and whether you’ll need extra power generators. If your shoot involves any special effects, you’ll want to take extra care in planning the lighting for those shots.
Controlling the Quality of Light
In addition to having different color temperatures, lights have different qualities. They can be direct or hard, they can be soft or diffuse, or they can be focused, like a spotlight. Figure 6.6 shows the same subject lit with a diffuse key light (top) and a hard key light (bottom).
There are many types of lighting accessories that can be used to control the quality of professional lights. A special Fresnel lens attachment lets you adjust the angle of the light beam from flood to spotlight (see Figure 6.7). Barn doors attach to the light itself to help you control where the light falls. Round scrims fit into a slot between the light and the barn doors and allow you to decrease the strength of a light without changing the quality. Single scrims (with a green edge) take the brightness down by one-half f-stop, and double scrims (with a red edge) take it down a whole f-stop. (See Chapter 7 for more about f-stops.)
nLighting gels are translucent sheets of colored plastic that are placed in front of the light, not only to alter the color of the light, but also to decrease the brightness (see Color Plate 12). The most common use of lighting gels involves converting tungsten to daylight or vice versa. Diffusion gels are usually frosty white plastic sheets that make the light source appear softer. Gel frames allow you to place lighting gels behind the barn doors, but it’s usually easier to use clothespins to attach gels directly to the barn doors.
nBounce cards (often just pieces of white foam core) are also used to create soft, indirect lighting, while reflectors (shiny boards) are used to redirect lighting from a bright light source, such as the sun.
nC-stands (short for Century stands) hold flags, nets, and other objects in front of the lights to manipulate and shape the light that falls on the subject. We’ll talk more about how to use these items as we cover traditional interior and exterior lighting.
130 The Digital Filmmaking Handbook, 4E
Figure 6.6
The choice between a hard or diffuse key is an aesthetic one.
This actor is lit with a diffuse key (top) and a hard key (bottom).
Lighting Gels
Gels are an indispensable tool if you’re serious about lighting. Rosco and Lee make swatch books like the one in Color Plate 12 that contain samples of the different gels they produce. Gel swatch books are usually available at any professional camera store.
Colored gels can be used to add just about any color in the rainbow to your light sources. It’s a good idea to have a choice of colors on hand. Remember that the brighter the light shining through the gel, the less intense the color will be. Adding colored gels will always decrease the brightness of the light.
Color temperature orange (CTO) and color temperature blue (CTB) gels can change the color temperature of a daylight-balanced light to tungsten, or tungsten to daylight.
Neutral density gels cut down the intensity of light without changing the color temperature. These gels are extremely useful when shooting video, where too much light is often a problem. They are especially handy when it’s necessary to shoot in front of windows.
Diffusion
Because digital video can have a “hard” look, using softer, diffuse lighting is increasingly popular, and there are a range of tools and techniques to add diffusion. The simplest way is to cover the lights with diffusion fabric. Diffusion gels, as mentioned previously, can be clipped to the barn doors on the light itself. Special diffusion bags, like the one on the HMI light in Figure 6.3, are designed to fit over the light entirely. Large silks are special diffusion fabrics that fit into a frame that you place in-between your lights and the subject. In addition, you can also use fog machines to create a smoky, atmospheric haze in the air itself.
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Figure 6.7
These tungsten lights by Arriflex range from 200W to 1K and are each equipped with a Fresnel lens to allow for focused or flood lighting.