Light is one of the keys to great photography. Mastering the use of light calls for understanding several important principles. One of those is using the direction the light is traveling in to your advantage. Novice photographers worry about whether or not they have enough light to make a photograph. Experienced photographers know that is the least of their concerns. Used properly, light direction can make your images more dramatic, more striking and more interesting. Let's take a look at what directional lighting can do for you.
Showing detail
Directional lighting can reveal detail that "normal" (overhead) lighting can't. Lighting a subject from the side fills in some areas and creates shadows in others creating depth and showing contours. Often a pair of lights are set up at 45 degree angles to the subject for close up and macro photography to show detail as completely as possible.
Dramatic lighting
Directional lighting can add drama and mystery to an image. Narrow side lighting (using a barn doors, snoot or gobos) can give a sense of the subject being hidden in the shadows. This careful control of lighting can hide and reveal exactly what the photographer wants the viewer to see.
Backlighting the subject can cause a silhouette, which simply reveals the shape of the subject without showing the detail, creating even more mystery. Another version of this is known as "rim" lighting. In this case a light is directed towards the subject from behind, while another light illuminates the front of the subject. With careful control of the output from each flash it's possible to create a glow around the subject from the backlight.
"Ghoul" lighting is another version of dramatic lighting. If you've ever watched an old black and white horror movie, the unearthly lighting on the vampire or monster was made using this technique. For Ghoul lighting simply position the light down low pointing up towards the subject. The light direction and shadows will be shown in the opposite direction we're used to seeing them travel in and create the otherworldly unnatural effect.