Questions to consider when recreating lighting scenarios for photo-realism (Light Matching)

Here are some questions you have to ask yourself to obtain the information needed to light a photographic environment:

1. How bright is the scene? Is this brightness constant throughout the image?
• Some parts of an image may differ greatly in the brightness and generate the need to use many lights to recreate the brightness levels.
2. Is the scene inside or outside?
• Setting up lights differs greatly when trying to recreate indoor lighting from outdoors.
• When trying to match indoor lighting, it is important to know what types of light bulbs are being used. Each type of light bulb has a different temperature of operation and color pitch. Example: fluorescent light bulbs (long tubes) typically have a greenish or yellowish balance. Halogen lights have a more balanced white source but some have a bluish tint as well.
3. What type of light is being used? Sunlight? Moonlight? Artificial lights?
• It is important to know what types of light are being used so that you can use this information as a point of reference.
• How much light does the moon give objects at nighttime? Is the effect you are going for photo-realistic or a hyper-real version of reality? Which looks better on the screen: reality-based moon intensities or ‘adjusted’ nighttime lighting?
4. How many light sources are in use in the scene? Do you have to use the same number of lights to obtain the same results?
• Don’t confuse this question with bounce light. Yes, bounce light is a light source but it is not a main light source in some cases.
• Changes are, you will use just as many, if not more, lights in your recreations as your source image refers to.
5. What are the surfaces made of in this scene? Is one surface polished wood while another is rusty metal? Is the scene dominated by old brick or painted concrete?
• Knowing what type of material is in the scene helps figure out the need for lighting intensities and where and how much bounce light you need to generate.
• Enough though an old brick wall looks great and has lots of rich red colors in it, it may not cast off much light because of how much light is being absorbed. Think about the material’s ability to absorb light.
6. How many bounce lights do I need to create?
• Unless you are using some sort of Global Illumination engine (such as Mental Ray), you will need to figure out how many bounce lights you will need to set up.
• General rules about bounce lighting:
  • Bounce light is never as intense as the source.
  • Bounce light takes on a color tint/shade of whatever material is suppose to be bouncing off of.
  • Bounce light fades in intensity as it goes further from the source.
  • Bounce light can, and often does, produce shadows. However, these shadows may be extremely faint and hard to make out.
7. What are the intensities of the lights used in the scene?
• Can you measure the intensities of light at the time you record the source image?
8. What time of day is it?
• This will help determine how bright some lighting scenarios will be.
• The time of day can also influence how warm or cool lighting scenarios.
9. Does weather play a factor in the lighting?
• How does lighting scenarios vary from a sunny day to a cold wintry storm?
10. Is color balance needed?
    • Do you need to color balance for video, gaming or web?