Ever whip out your camera, line up your friends for a photo and suddenly realize you don't know where to stand with the camera? I have. When it comes to the direction of light, there are 360 degrees of possibilities, so when the natural or artificial light source isn't working for you, it's best to change it by moving your position, your subject's position, or the light itself. Knowing how each angle will affect the final photo is the first step to becoming the next Annie Leibovitz.
High front light (sunlight)
We are trained early on that high front light is the best type of light, and often it is. The pro of high front light is the fact that the scene will be well lit and that the colors of the scene will be extra bright. The negative aspect of lots of sunlight in a picture is that your subject may squint and very high sunlight (seen at noon) will create deep shadows under eyes and chins, unless you use fill flash.
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Front lighting illuminates the portion of the subject facing the photographer. Your camera's flash is the most common type of front lighting. It's great because it provides the most information to the camera by lighting the entire scene. It's also the easiest type of light to deal with photographically because there are fewer shadows to confuse the camera's light meter. The trouble is textures and details are minimized and scenes appear flat with few shadows.
Side lighting is great when you want to emphasize texture, dimension, shapes, or patterns. Side lighting sculpts a subject, revealing contours and textures. Use side lighting to exaggerate dimension and depth. At a 45-degree angle to the side, it's one of the most flattering types of portrait lighting. It can separate the subject from the background. Problem is, it may be too severe for some subjects, creating some areas that are too bright, and some that are too dark.
Light that comes from behind your subject is by far the trickiest to use, but the dramatic results may be worth the effort. Back light is great because it simplifies a complicated scene by emphasizing the subject, as in a silhouette, it also provides a flattering halo of light in portraits. You do have to be careful as it can cause lens flare resulting in low contrast and strange light spots across the picture.