By placing the Key Light in different positions
relative to the subject various moods can be
achieved. This will be discussed in more depth
in the Time of Day and Mood section. For now
let's just look at a couple of common lighting
schemes.
Camera angles used in conjunction with lighting angles
go far in creating a specific look for a scene.

• 
  Low Angle: A Light that come from
  below the subject is often referred to
  as a "Light From Hell." Evil
  characters are lit this way and it instantly
  reminds us of flashlights and campfires.
  

• 
  High Angle: A light that comes
  from directly above the subject can be
  really creepy. Whenever eyes are in shadow
  it gives a strange feeling. A dim fill
  light can partially reveal the eyes are
  dark shadow areas.
  

• Back Lit: A Light that come
  in from behind the subject is called, you
  guessed it, a back light. So the Back light
  takes the place of the key light as the dominate
  source of light in a scene. This is great
  for creating a silhouette of a character
  and creates a mysterious feeling.
  Part 3: Key-to-Fill
  Ratio
  
  Key-to-Fill ratio is
  a simple equation that describes the relationship
  between the Key light and the Fill light. A key
  light that is twice the brightness of its fill
  light has a Key-to-Fill ratio of 2:1. This ratio
  would be considered a Low Key-to-Fill ratio.
  A scene with a ratio of 18:1 would have a High
  Key-to-fill ratio.
  
  Low Key-to-Fill ratios
  are most often used to depict a snow or overcast
  day or bright interiors. Shadows would be washed
  out by the reflected light. Typically Low Key-to-Fill
  ratios create more of a happy lighting scheme.
  When you are buying your Super Slushy in the
  Quicky-Mart you are in a Low key-to-fill ratio
  environment. We will be discussing ways in the Time
  of Day and Mood section on how to create
  more gloomy lighting using lower ratios.
  
  High Key-too Fill ratios
  can be used for bright daytime light with dark
  shadows, night scenes or to build suspense
  and drama through severe lighting. This technique
  of using high ratios is best seen in Film Noir.
  
  The well executed use of these
  techniques can go greatly to enhance mood and
  suspense throughout a scene or sequence. Remember
  that continuity from scene to scene is important,
  as well as the use of temporal contrast
  to enhance a change of location or even the story
  conflict.
  Part 4: Quality of Light
  and Color Balance
  
  Without getting to deep into
  color theory I would like to discuss Quality
  of Light and Color Balance.
  
  There are only two real Qualities
  of Light, Soft and Hard. Thus
  creating two types of shadows, soft and hard.
  We can also call it sunny or cloudy. The hardest
  light would be generated by the sun on a very
  clear day, and the softest light would be created
  by the sun on a very overcast day. It is the
  millions of particles floating in the air that
  bounce and catch the light. These particles then
  refract, reflect and scatter the light from the
  sun creating all the wonderful variants of light
  we see everyday. The more the light bounces around
  and gets diffused, the softer shadows become.
  This is also the cause of atmospheric perspective. Atmospheric
  Perspective is the viewable phenomenon of
  things getting bluer or less saturated and fuzzier
  in the extreme distance. The diffusion of light
  in the air is what we can sense, even if we are
  unaware of it happening. The ability to control
  this gives the artist explicit control over the
  feeling of a scene. We will keep these two qualities
  of mind when we talk about Time
  of Day and Mood.
  Part 4: Quality of Light
  and Color Balance
  
  Colored lights can be very powerful,
  but can also get out of hand very easily. When
  using colored lights, try to stay away from saturated
  and dark colors. That said there is always a
  time and a place for vibrant lights, just keep
  in mind that is not very natural.
  
  The color of a light, on film,
  greatly effected by the balance of that film.
  Because in 3D graphics there is no film actually
  being exposed we need to simulate it. On a side
  note: It is a strange phenomenon that people
  perceive an image that has all the flaws, distortions
  and artifacts of film to be more "real" that
  a well light and clean render. So where does
  that leave us? Well, we try to approximate what
  the camera lens is seeing, in order to accommodate
  the tastes of our audience. Of course, a chosen
  style should prevail.
  
  For simplicity sake we will
  focus on two different types of balanced film. "Indoor" or
  Tungsten-Balanced and "Outdoor" or
  Daylight. There are other kinds of film and gels
  and filters and post effects that all can contribute
  to the overall color of a scene. A good thing
  to keep in mind, is that the dominate light source
  in the scene should dictate the balance of the
  film. The balance that is referred to is on the Kelvin
  Scale. It is a scale that measures color
  temperature. The range of the Kelvin scale is
  from 0K - 10000K. The higher the temperature
  the bluer the color and the lower the
  temperature the redder the color. An
  Outdoor film would be balanced for 5500K
  and an Indoor film would be balanced for 3200K.
  
  So what does the light balance
  of film mean to a CG artist? It means that in
  a "balanced" light set up, the
  dominant light source would be close to white,
  all others would range from warmer to cooler.
  For example: In a daylight balanced scene, the
  sun would be a very pale yellow and the light
  from the sky would be a light blue. You knew
  this already? Well how a bout an indoor scene
  lit with a torch near a doorway to the outside?
  With an Indoor balanced scene the torch would
  be a pale orange while the sunlight from the
  doorway would be bluish.
  
  A final word about Quality and
  Color. These, like all the other principles that
  are being discussed in this guide, are only part
  of the equation and are in no way absolute. Let
  story and character drive your lighting set ups.
  Not the other way around.
  
  We will talk further about overall
  lighting pallets in the Time
  of Day and Mood section. There
  we will go more in depth about tinting a scene
  to convey emotion.Part 5: Time of Day and Mood
  
  To convincingly convey Time
  of Day and create a Mood all the
  principles, rules and tricks we know will now
  come into play. This is where it all comes
  together and stories are told. A well planned
  light set up will establish Time of Day, Seasons and
  even the Emotional State of the characters
  involved in a scene. In this Section we will
  discuss techniques used to believably create
  a scene that pushes forward and supports the
  story.
  
  Most likely the main light source
  of an outdoor scene is going to be the Sun. It
  is a well known fact that the Sun rises in the
  east, arcs through the sky and sets in the west.
  This makes the decision where to put the key
  light when the time of day is known. But, please
  don't be to strict a bout where the sun is placed
  tin the scene. Aesthetics and a well light scene
  are more important than a astronomically accurate
  representation of the sun. No one will notice
  if we fake the sun position if the scene looks
  good.
  <table align="right" border="0" cellpadding="5">
  <tr>
  <td align="right">
  
  
  
  
  
  
  
  
  
  This image shows a possible
  representation
  of Time of Day.
  </td>
  </tr>
  </table>
  
  Morning light tends to be a light
  blue with a pale pink sky or fill. The shadows
  are long and crisp. The sun itself will be a
  very orange and fade quickly as it rises to more
  of a pale yellow. Light from the sun bends quite
  a bit as it travels through the atmosphere and
  it shifts color more and more as it nears the
  horizon. However, in most cases, there is very
  little atmospheric perspective visible during
  the very early hours of the day. This is due
  to the fact that the dust has literally had time
  to settle in the inactivity of the evening. Dawn
  has a distinctively different look than Sunset
  because of this. Emotionally the morning represents
  rebirth and optimism. A use of bright colors
  both in the light and shadow will bring across
  that feeling of crisp cool air of the morning.
  
  As the day goes on and the Sun
  reaches its apex in the sky the rays of light
  are traveling through the atmosphere nearly perpendicular
  to the ground. This means that the light won't
  bounce around and bend as much and its light
  is closer to a bright white. The shadows are
  dark and colors seem muted in the bright light.
  The term "high noon" evokes a lot of
  feelings. There is nowhere to hide in the relentless
  rays of the bright daytime sun. In winter, however,
  the sun would be much lower and pushed more towards
  the blue.
  
  Finally the sun begins to set
  and the color of the light becomes more and more
  red. The shadows stretch out and are blue or
  purple. Because of the activity during the day
  and the increase of particles in the air, sunsets
  are very orange and red. The hours preceding
  sunset are used in film quite often. It is because
  of the vibrant and rich colors that are present
  in the late afternoon.
  
  The sun is gone and the stars
  and moon are the only natural light sources.
  Now that night has arrived this is no excuse
  to ditch color. . Nighttime can be full
  of color, just mostly blue. But if we accent
  it with warm manmade practical lights we can
  get a full and rich palette for our scenes. Also,
  keep shadows sharp and have a high key-to-fill
  ratio to enhance the feeling of night.