By Audri Phillips
Ultimately, lighting is about controlling and shaping light and shadows, reflections, refractions, and even color-whether you do it on a computer or on a film set. This kind of control requires an understanding of how light works, the aesthetic art of lighting, and techniques for lighting. This knowledge helps you develop your eye so that you can look with understanding at your image, clearly see it, and know what needs to be done. By looking and learning as much as you can about color and lighting, you can decide which information to use to create your lighting design-be it naturalistic or stylized in a myriad of ways.
Though the tools may differ, the principles involved in creating good lighting for computer graphics are used on film sets, as well. This article, although primarily about digital lighting on a computer in a 3D package, refers to lighting in other environments, as well. When I refer to settings in a 3D package, I mean Autodesk* Maya*; however, most other 3D packages have settings for these same attributes, although their interfaces may be different.
Looking and Learning
When I was given my first storyboarding job on a feature film, I had no idea what to do, so I turned on my TV and started drawing the images as they went by. Not only was there information on how to put images together to tell a story, but there was also a wealth of information on lighting and lighting design and how lighting can help tell a story. For a computer graphics (CG) artist, understanding how light works in the natural world is important, because not only will you be called upon to produce naturalistic-looking imagery, but sometimes you will be asked to marry live-action footage and computer-generated imagery. Also, like a cartoonist who understands form and anatomy, if you want to stylize your lighting design, you need to understand which lighting attributes and qualities to work with. So, look at the world around you and study it (see Figure 1).
Figure 1. Have you ever noticed how much more reflective a tide pool is around sunset, when it seems you can see the whole sky reflected in it, than earlier in the day? Look at the play of warm to cool colors in this photo.
In lighting, darkness is just as important as light. This darkness can be caused by the absence of light (shade) or by an object blocking the light (shadow).
Shadows and Composition
How the shadows fall in any scene you are lighting contributes to the composition as well as the mood. Most often, to create the shadow design composition, you want only the key light (that is, the primary light source) casting the shadows. But there will be times when, in the interest of true realism, you will want every CG light in a scene that represents a practical real light to cast a shadow. For example, you may want all of the CG lights representing table lamps in a living room to cast shadows so that as your character walks by them, the shadows change.
In Maya* and most 3D animation packages, it is easier to control shadows than it is on a film set. You can selectively turn the shadow casting off on a light or change the render setting on an object to make it such that it does not receive or cast shadows (see Figure 2). On a live set, to get rid of unwanted shadows from a light, you must employ techniques such as bounce cards and diffusion filters.
Figure 2. Light and shadow can create both mood and composition, and you can use light as a powerful metaphor. Light by its very nature is symbolic to us. I took this photo in a dance studio-an appropriate place for an inspirational ceiling.
Shadows and Time of Day
Shadows are one big indicator of the time of day. Shadows late in the afternoon when the sun is low on the horizon are longer and softer versus the shadows at high noon, when the sun is directly overhead. At noon, shadows are shorter and sharper. That is one reason noon sunlight is referred to as hard, and late afternoon light is soft. Experiment with shadows by holding any light source lower, and then higher-directly over an object-and watch how the quality of the shadows changes.
Moving Shadows and Light Patterns
Moving shadows can help add to a sense of restlessness, danger, or suspense. Think of someone tossing in bed with shadows falling over him or her or shadows indicating an otherwise-unseen presence. You can break up the throw of a light using various devices. You've probably noticed the stripes of light coming in through Venetian blinds, for example. Walking at night, I often wonder at the dappled light and leaf shadows on the pavement caused by the street lamp light shining through the trees. Have you ever looked at beautiful cloud shadows traveling over mountains?
Figure 3. When I light, I sometimes I like to do what I call overlighting, or really pushing a tonality change-a great contrast in tonality that often exists in life. Overlighting can actually add to the naturalism of your lighting. Look at the hot white lighting on some of that foliage: Go for the drama!
On a film set, you can place a gobo (also known as a cucoloris or cookies) in front of a light to reshape it. Gobos are usually wood cut into various shapes blocking the throw pattern of the light, sometimes to imitate broken-up light and shadows. In working with lighting in a computer 3D package such as Maya*, you do the same thing using what is known as mapping on the intensity or the color of the light-usually a spotlight.
Outdoors, the main source of light is the sun. Its rays come down to earth from one direction. You can think of the sun as the key light, because it is the dominant light outdoors. You can think of any light that is the dominant light in a scene as a key light, although a key light is generally used to highlight and add dimension to the main subject in a scene. The key light is generally the first light you set up, and it is part of the commonly used three-point lighting set up. It is the light that really sets the mood of a scene.
The key light in a scene can be animated, or it can constantly change as your character moves. Sometimes, you might want your character to be moving in and out of the light to add a sense of distance and depth or drama to your scene. Other times, you may want your character to be in the light at all times, so that nothing he or she is doing is lost. In a scene, the key light can be constantly changing, as for example when your character moves from under one street lamp to under another.
Reflected and Absorbed Light
Subjects can be lit by direct illumination from a light source as well as from reflected light. One of the most important things to understand about light is that some of it is reflected off of or absorbed by every surface it hits. In life, light can be reflected off one surface, then hit and bounce off of another surface again and again. Outdoors, the light from the sun creates a lot of bounce light.
Besides adding to the general brightness and illumination of a scene, this reflected light creates highlights, spectral and diffuse light, as well as reflections such as you see when you look in the mirror. This reflected light also has a lot to do with the colors you see and color bleed.
Calculating every light bounce is a lot of information to retain in a computer's memory, so 3D packages have come up with less memory-intensive ways of emulating this process. Some of these systems are called Global Illumination (GI) or radiosity, but there are many even less memory-intensive ways to emulate light reflection. Cheats can be as simple as making a cluster of directional lights aimed in different directions (see Figure 4).
Figure 4. You can put colors on the lights to reflect the colors in the scene. Generally, a ground plane is warmer, so the lights pointing up from the bottom would have warmer colors on them.
You may have heard the term ray tracing. A ray trace light on a computer gives you the calculation of one bounce back from a surface toward the camera. This one bounce is enough to give you a reflection.
A computer rendering/lighting system that just measures the direct illumination of a light is called ray casting. In ray casting, there is no reflecting or refracting of light. It used to be that this functionality was all rendering packages were capable of. Now, the ray casting is usually just the first calculation of light a renderer in a 3D package would make.
The quality of light-whether it is hard or soft-is important in lighting, contributing to the mood of a scene. It is easier to control whether a light is hard or soft on a computer than on a live set.
The sun is obviously our largest light source, but because of its great distance away, by the time the light rays reach us on a clear, unclouded day, they are virtually parallel, making it a hard light source. Parallel rays (or close to parallel rays) are a characteristic of hard lighting.
Hard light creates crisp, dark, and harsh-edged shadows, emphasizing angles and edges. Hard light is good for showing contrast and giving dimension to a subject, a landscape, or an object. It's also good for showing form and volume. Hard lighting can show texture very well, as in leather or an engraving, and it's good for lighting night scenes, where you want dark, hard-edged shadows. On set, hard light can come from a point source, such as a naked light bulb or a focused spotlight or a small, focused source such as a Fresnel lens.
In a 3D program, a good hard light source might be a light that starts from a single point, such as a point light or a spotlight with the penumbra set to 0. Hard light has no soft falloff. A directional light, which is the closest light to the sun in most 3D programs, also provides a good hard light source. Like the sun, the directional light sends down parallel rays of light at the same angle over the entire scene (see Figure 5).
Figure 5.Notice the highlights caused by this focused hard light source. I have used only one spotlight as the key light, and there is no fill light to soften the lighting.
When light rays from the sun hit a heavy cloud bank, the clouds can act like a diffusion material, scattering the rays in different directions and creating a softer light. On a cloudy day, some things will be brightly lit and others not (see Figure 6).
Figure 6.I took this photo on a walk at lunch when I was working for DreamWorks Feature Animation in Glendale, California. The light in the valley could sometimes be extraordinary.
The term soft light refers to a light that wraps around objects and creates shadows with soft edges or (ideally) no shadows. The rays of a soft light are less parallel to the illuminated object than the rays of a hard light, illuminating an object from multiple directions, so a soft shadow or no shadow at all results. A soft light is a flattering light for a portrait, lessening the contrast of wrinkles on a face. It reduces texture and smoothes an object's surface. The danger of soft lighting is that it can leave the subject a bit dimensionless (see Figure 7).
Figure 7. Here, I have used a key and fill light to create a softer look. Because I did this in Maya*, I was also able to turn off the emit specular and the shadows on my lights to help create a softer lighting on the face.
In Maya, a good soft light is an area light. In an area light, the light is not emitting just from a single point but from many points, thus spreading the light out. Area lights come in many shapes, and you can change their sizes. A bigger area light will emit light from a larger area. You can even make a spotlight into a soft light by increasing its penumbra and turning off its shadows. You can also make lights softer by turning off their shadow casting. A global illumination system or radiosity can produce soft lighting (see Figure 8).
Figure 8. This room is filled with soft lighting coming in through the windows. Most of the room is being lit by softly reflected light rather than a direct hard light source. Notice how the light varies on walls and all surfaces in the room. This is what radiosity on a computer tries to emulate-all of the reflected and bounce light.
You've set up your key light, but now you decide that you want to add more light to the scene. The first light typically added is called the fill light. Fill light is generally a soft light that doesn't cast shadows.
The fill light adds light to the scene, softening the light from the key light by lowering the contrast of the dark to light areas. Often, a fill light is set up lower than and opposite to the key light, on the other side of the camera axis, pointing toward the object to be illuminated. Fill lights are usually low, as they are often emulating the reflected light that would be coming off the floor. You can use bounce light to add to the fill light.
Generally, when you are lighting a realistic or naturalistic scene, you do not want any totally black areas in the scene. In life, there are rarely any areas of complete black: Some light has bounced in. Fill light can help provide this light. Even when I am lighting a night scene, I try to add some light so that no area is totally black.
Key to Fill
You may have heard the terms key-to-fill ratio or low key and high key lighting. A key-to-fill ratio is just a measure of the brightness of your key light to that of your fill light. If your key light is 3 times as bright as your fill light, that's a 3:1 ratio. The expression high key lighting or low key lighting refers to the amount of fill light in your scene.
Using Lights to Set Up Moods
In a bright and happy scene-a comedy, say-you would be well served by high key lighting. A brightly lit scene with low contrast can create a safe feeling, as nothing is completely hidden in shadow. The mood is calm and tranquil; no danger lurks. In contrast, a lot of cool florescent light can make a scene seem sterile. Cool-temperature high key lighting could be good for creating a scene in a drug store or laundromat, for example.
With high key lighting, because of the lessening of contrast, a scene can look a bit flatter. To give volume to an object or scene, you want that contrast of dark to light. A night scene is a good example of low key lighting. Low key lighting is also used in a film noir lighting style-a popular film genre and lighting/cinematography style developed in the 1940s and 1950s in American films. It speaks of danger and suspense with a touch of evil. In a film noir lighting style, darkness and shadows predominate: There would be very deep black shadows and light falling exactly where you want it to, with very little light spill. On the other end of the low key lighting spectrum, consider a romantic dinner scene: Soft, flickering candlelight can be sentimental or romantic. Candles would also work in a church scene.
A third type of light commonly used in a three-point lighting setup is the back light, sometimes referred to as a rim light (see Figure 9). When the sun is lower in the sky, its rays can put rim lighting around people and objects out in the landscape, separating them from the background. Back lighting is a device you might want to try out in your lighting to help emphasize a figure or object. Often, you set up a back light to illuminate a subject this way. If there is already enough contrast between your character and the background, you might not want to use a backlight to rim and define your character's edges.
Figure 9. A three-point lighting setup illustrated in Maya*
This article talks about both the art and science of lighting, touching on many of the basic characteristics of light and some of the lighting tools and lighting setups you can use in a 3D program to emulate them. Ultimately, you want to use light as an art to play a part in the storytelling and emotional quality or mood of a scene. This subjective process is the contribution you as an artist can make.
The second part of this two-part series will discuss the relationship between color and light-from the science of color and light to how you can use color to create depth and emotion.
About the Author
Audri Phillips is a Los Angeles-based artist currently working and exhibiting in a variety of media ranging from computer animation and motion graphics to her more personal work-oil paintings and video art (visual poetry). She has worked for more than 25 years as an artist/digital artist in the entertainment industry in Los Angeles at such studios as Disney Feature Animation, Sony Imageworks, DreamWorks Feature Animation, Rhythm and Hues, Digital Domain, and Electronic Arts as well as a number of small design boutiques. Her production experience includes art direction, design, visual development, storyboards, and color and lighting. Examples of her work are available at http://www.audri.com, http://www.alternatesight.com, http://visualmusic.ning.com/profile/AudriPhillips?xg_source=profiles_memberList, http://www.absolutearts.com, and http://www.lynda.com.