All about Light

More helpful information (thanks to the internet)

Color of Light
The color of daylight has a profound effect on the atmosphere of a photograph, and knowing how it affects the emotional content of an image enables you to control the mood of your photos. Changes in daylight's color occur most rapidly--and are most dramatic--at the beginning and end of the day, so work quickly at these times if you want to capture a particular mood.

Light Quality
Is it the hard light of a blistering sun streaming down from a clear, cloudless sky? Or the soft, diffuse light of a hazy sky soothing your subject in a soft embrace? Hard light blasts its way across the landscape, zapping subjects with brilliant highlights and creating jet-black shadow areas. Soft light awakens worlds of subtle hue and gradation and provides a gentle but pleasant modeling in both landscapes and portraits. Because you can't alter the quality of light (other than by waiting for it to change), the key is to match it to a compatible subject: hard light to accent the graphic lines of an industrial landscape, or soft light for a group portrait.

Direction of Light
The direction from which light strikes a scene, relative to the camera position, has a significant effect on color, form, texture, and depth in the resulting photo. Frontlighting spills over your shoulder and falls squarely on the front of your subject. Because frontlighting is very even, auto-exposure systems handle it well. It produces bold, saturated colors, but when too strong can actually wash out some colors. The downside is that, because all the shadows are falling behind the subject and away from the camera, frontlit scenes lack a sense of depth or three-dimensionality.

Sidelighting comes from the left or right of a subject. Because the light is scraping across from side to side, it catches every surface blip and imperfection, leaving a trail of large and small shadows and exaggerating surface textures. It is ideal for landscapes, like desert badlands or beaches, where you want to convey the tactile qualities of a subject. Sidelight also imparts form and three-dimensionality to objects, giving a pumpkin its full roundness or a tree trunk its volume. Gentle sidelighting, especially from slightly above, works well for portraits because it creates a delicate modeling of facial features.

Backlighting can produce theatrical effects, particularly with landscapes. Shadows coming toward the camera exaggerate depth and distance and help lead the eye into the scene. When backlighting is used behind partially translucent subjects, like leaves or human hair, it creates a bright fringe called rim lighting that helps separate subjects from their surroundings. In backlit portraits, however, you may need to increase exposure by 1 to 1 1/2 stops over the metered value to keep faces from being lost in shadow. An alternate solution is to use flash fill. Keep the sun itself out of the frame or it will trick the meter into severe underexposure.

With many subjects, you can change the apparent direction of lighting by changing your shooting position--by taking a short walk if you're shooting a close-up of a barn or a horse, or a drive if you're shooting a landscape.