This second part of a two-part series on lighting basics is devoted to the basics of color in lighting. It touches upon the multiple ways color and lighting are inextricably linked-from the science of color and light to how you can use color to create depth and emotion. Part 1 is: The Basics of the Art of Lighting: Simple Principles of and Techniques for Creating Artful Lighting.
Color and Light Are Inextricably Linked
A rainbow breaks sunlight into its color spectrum when sunlight is refracted in the small droplets of water that are in the air. The droplets of water act as a prism, bending the light. White light is the full spectrum of light. As it goes through a prism, the light is bent and sent in different directions, breaking the light ray into all of its colors, including the color groups of red, orange, yellow, indigo, and violet-the visible spectrum of light.
Refraction of Light
Light goes through air in a straight line but changes speed and direction when it goes from one material to another, such as through air and then water, a lens, or a prism. This behavior is called refraction. There is an index of refraction, which is a measure of how much the speed of light is reduced inside a medium. A diamond refracts light, which gives it its beauty when the light bends as it travels through the diamond, and there is an index of refraction to measure that. A diamond has an index of refraction of 2.417, while the index of air is 1. You can use this number in a 3D program to help give a material its correct look, making it refract light properly. For example, in the Mental Ray renderer in Autodesk* Maya*, the dgs_material has an Index of Refraction attribute (see Figure 1).
Figure A. In this Maya* attribute editor for the Mental Ray dgs_material, note the Index of Refraction box. The default value is 1, which means that the light is not bending as it travels through an object.
Caustics also are caused by light being reflected off or through a curved surface. A rainbow is actually the result of multiple caustics caused by the water drops in the air. Caustics are best known as the patterns of light on the bottom of a swimming pool. Photon mapping is one of the best ways to simulate caustics.
Reflected Light and Color
Reflected light has everything to do with the colors we see. Light rays are either reflected or absorbed. The color of an object is determined by the light rays reflected off of it. An orange fruit absorbs all the light except the orange light it reflects back at us. A banana reflects back yellow. Shining a yellow light on a scene with a lot of blue in it will not make the scene look lighter (see Figure 2).
Figure 2. I used the same colored spheres and lit them with different colored lights. The spheres could only reflect back the colors that were in them. For example, when the red sphere had a blue light on it, it could reflect back nothing and so appears black.
A purely black object reflects back no light but absorbs all the rays. Have you ever noticed how a black object in sunlight can be much hotter than the white object right next to it in the same sunlight? I live in Los Angeles, so I tend to lean toward buying light-colored cars for that reason. There is a relationship between the color of light and its temperature. Light, after all, is energy.
Color Helps Create Mood
The color palate of lights you choose can help set up the emotions of the story. Purple has always been associated with royalty, while yellow is considered cheerful and happy. White can stand for purity, pink is associated with femininity, and brown is earthy and practical, while black is formal and elegant. Grey can be oppressive and dreary-a good color for a prison or a story about someone who is depressed. A blue light can make something appear moody or sinister. Blue may be good lighting color for a nightclub. Color can also clue you in as to location. Certain locations in a film, for example, could be lit with one palate of light, and another location with a different palate. Such lighting can help with a story's theme.
Although the altitude, angle, and color of light changes with your location, orientation, time of day, and season-an important element in telling a story-you don't have to get that scientific about it to convey such information. In general, at dawn, you may have noticed that the light is cooler, bluer, and it warms up as the day progresses so that by noon, the light is white. By sunset, the light appears much warmer, redder.
Certain computer programs have lighting systems for calculating the position of the sun for you based on a specific place in the world at a specific time. Coming in through windows, the light from the east is of course strongest in the morning, with strong, crisp shadows. Because the light is whiter, colors are rendered more accurately. Daylight from the west is strongest in late afternoon and early evening, so shadows from it are soft and long, and the light color is a warmer red to gold. Daylight from the south is more dominant from late morning to mid-afternoon.
Creating Depth with Light and Color
In computer-generated imagery, you usually want to give the illusion of depth and dimension. To do this, look at the clues you're given in the world around you, and then try to emulate them. The color, direction, quality and intensity of your lights, as well as the color of the object surfaces, and how they receive light all aid in creating depth and dimension. Atmospheric effects such as fog also aid in creating the illusion of depth and dimension. It is very easy in computer graphic imagery to create a scene that looks flat and dimensionless. One of the biggest causes of this is using a light source that is directionless, that evenly lights your scene from every direction. This is known as an ambient light and can be found in most 3d packages but does not exist in real life. Use it sparingly and carefully. Sometimes people will use it to add in just a touch more fill light to brighten the entire scene. Another important clue we are not discussing in this article is related to depth of field, which part of a scene is sharply in focus and which is not, but this article relates more to camera lenses, their focal length and the object distance from the camera.
Color in Night Scenes
As a convention, blue light is often used to denote a night scene. At night, moonlight may be a cool light, but lights on a building can be warm or cool. Look around a street at night and notice the beautiful play of colors caused by the mix of warm and cool lights. Also note that specular highlights and reflections become even more noticeable and glaring at night.
Warm Colors Come Forward, Cool Colors Recede
In life, no color is exactly the same at different distances. For instance, that exact red you see in the foreground you will not see in the background. A good way to create depth in a scene is to contrast warm and cool light. Try lighting the foreground with a cool light and the middle ground with a warm light. I remember the teacher in my first water color class saying that if you paint warm tones in the foreground, paint cool tones in the middle ground, and this will create depth and separate the two areas.
Lighting Foreground, Middle Ground, and Background to Create Depth
Another way to give real sense of depth to a scene is to divide it up into imaginary horizontal planes that recede from the camera, and then light each plane differently (see Figure 3). Try making the foreground dark-dark trees, for example-then make the middle ground light and the far distant background more of a middle brightness. You can add a fog bank in the distance to further separate the background.
Figure 3. Notice the different light conditions in this image. There are three major horizontal planes of light: dark bars in the foreground, a brighter middle ground, and the darker background. Then, there is the brightest light in the image: the window plane on the right.
Pools of Light for Accents, Drama, and Depth
Another easy trick for creating depth is to set up pools of light that your character walks through as he or she moves away from the camera. Street lamps at night naturally set up such pools. Pools of light can add drama and focal points to your scene. I did some game lighting for over a year at EA, and a lot of our levels were illuminated with pools of light. Always remember that land is darker than sky-even at night-and that the horizon is the lightest part of the sky.
Light Changes on Every Surface
With a plane change, there is always a color change and a light intensity change (see Figure 4). For example, light strikes and reflects differently off each side of a cube, shifting color and light intensity on each side. As an experiment, hold up a small box and look how each side of it is lit differently. A give away that something is computer generated is that it is evenly lit on all sides.
Figure 4. I took this snapshot on a neighborhood walk. It's a good example of how with every change of plane there is a lighting and therefore also a color change. This is why it is dangerous to use the ambient light in a computer package, the light is coming from all directions equally and therefore everything is lit the same. Note that in Maya*, you can put some directionality on your ambient light, but it is best to avoid using the ambient light.
Lighting on Flat Planes
Look at a flat wall and notice how much the light and color of the wall change, even when you think it is being evenly lit. You want to achieve all this subtlety with computer lighting: Large areas covered with the same flat lighting are a sure giveaway they were created on a computer.
Warm and Cool Colors
As light travels around an object away from the light source, the light color will go from warm to cool (see Figure 5). Painters and comic book artists are known for playing with this effect, sometimes exaggerating it. Look at a Cezanne painting-at the color of an apple, warm and bright on the well-lit side and blue or cooler as it recedes from the light. It is like a turn around the color wheel. Shadows and shade are a cooler color than areas in the bright light. You can also use or exaggerate these light color facts to give your lighting a stylized look.
Figure 5. This building is being constructed from the same type of wood, yet look at the great change in color when the wood is in the light and when it is not.
Objects in the distance seem to get bluer the farther away from you they are. This phenomenon is known as aerial perspective. You can use this effect to create depth in your scene. The water in the atmosphere is picking up the light. Dust and water particles are invariably hanging in the air. Light traveling through these particles can create shafts of light. Smoke-filled rooms and foggy days are great mood setters.
Scale Is Important in Good Lighting
Light scale can also add to the visual depth cues (see Figure 6). To light a building at night, you want to use a lot of little lights. A building lit with one light will look like a miniature or give away that it was created on a computer.
Figure 6. This is early evening in Los Angeles, and not all the nightlights are on yet, but notice the number, size, and scale of the lights in the scene.
Visual Effects and Light and Color
Light and color play important roles in creating dramatic visual effects.
Light Color and Direction in Visual Effects
Light colors have everything to do with combining and compositing computer-generated objects into live-action film scenes-something that is done in most films. Think of a film like any of the Harry Potter series and how seamlessly all those fantasy computer graphics (CG)-created creatures fit into the live action. I worked on the first Spiderman film, and most of New York City Spiderman flew through was CG, as was Spiderman in some of those flying sequences.
Marrying the CG to the Live Action
You want to copy the light direction, angle, and color from the live-action scene to your CG object so that it will fit in seamlessly. If the light falls on your CG object in a different direction than everything else in the live-action scene, it will stand out like a sore thumb. The same applies to color. On a film set, there are techniques like shooting a white sphere in or near the place the CG object is supposed to go, and then giving that footage to the computer artist as reference. The artist can see the light direction and colors reflected onto the sphere. Other information, such as camera height, distance, lenses used, and where and what kind of lights were set up is also given.
A white object near an intensely colored wall seems to pick up some of the color of the wall. This phenomenon is known as color bleed, and once again it has to do with reflected light (see Figure 7). Some of the light being reflected from, for example, an intense blue wall is hitting the white ball and making it a bit blue. Everything picks up some of the reflected colors from objects around it. If you aren't using a radiosity renderer in your 3D package, an easy way to emulate that intense blue bleed light coming off the wall is to set up some small blue point lights by the wall.
Figure 7. Look at the color bleed on the leaves from the light being reflected off the orange. It is also a good example of warm colors in the light, cooler in the shade.
I hope this and the preceding article will start you looking more and searching for the answers as to techniques for conveying information and emotions with your lighting. Light by its very nature is symbolic: Endeavor to symbolize hope, despair, and everything in between in your lighting projects.
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.