Light is essential to creating a photograph. How a scene is lit will almost always vary from one photographer to the next, and lighting can help to determine a photographic style. Lighting can also convey mood. For example, if you want to show fear or add drama, you might use harsh shadows and keep the scene dark. If you're photographing children and you want a cheerful image, you might choose to have a more brightly lit scene, with a look of natural lighting.
The key is to know how light works, so you can be sure to have the correct equipment. You also need a good understanding of how your camera works, in order to make your images look the way you want. How you end up lighting your images is ultimately determined by your overall vision for the shoot, and it's important to try and "see" what the lighting will look like when you're planning for the photo shoot (see Figure 5).
Figure 5 For this image, I wanted the food to look as if it were plated on a "romantic" table setting. I typically shoot food images in diffused natural sunlight, but I needed to light this scene differently to match my vision.