Three-point lighting is a basic lighting technique commonly used in photography and television production. As the name suggests, it uses three different lights - key-light, fill light and back light. Here, we shall discuss these lights in detail.
Key Light
The main light -- the strongest -- has the most influence on the look of the scene. It is placed to one side of the camera/subject so that this side is well lit and the other side has some shadow.
This is a hard light source - placed to one side and up high.
Generally placed 45 degrees to the side of the subject and at a 45-degree angle above.
Similar to the light from the sun on a clear day, producing heavy, distracting shadows.
At least twice as bright as the fill light.
Fill Light
A soft light source.
The secondary light and is placed on the opposite side of the key light but closer to the camera, and at about the camera's height. It is used to fill the shadows created by the key. The fill will usually be softer and less bright than the key.
Can be positioned right beside the camera but it's safest to place it 45-degrees from the camera.
The fill light should be placed about 90-degrees away from the key light.
Usually, the fill light is at least half as bright as the key light.
“Fills in the shadows” by lowering the contrast between light and dark in the image, and it casts very soft indistinct shadows.
Back Light
A hard light source like the key, but placed behind the subject, again at about a 45 degree angle above and behind the subject. Makes the subject stand out from the background.
Sometimes referred to as the “highlight” or “hair light” as it is often used to give a sheen or highlight to an actor's hair.
Should be placed directly behind the subject in relation to the close-up camera.
If a back light is placed too far to one side, light will spill around one side of the subject and leave the other side dark.
The brightness of the back light depends on the reflectivity of your subject. For example, a person with blond or gray hair needs far less back light than someone with brown or black hair.
Rather than providing direct lighting (like the key and fill), its purpose is to provide definition and subtle highlights around the subject's outlines. This helps separate the subject from the background and provide a three-dimensional look.
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