The key light

In a scene, the primary light source is often called the critical light. Critical light does not have to be just a source of light, but it must be the primary source of illumination. Similarly, the critical light is not necessarily fixed in one place like a point light source.

Although THE point light SOURCE IS USUALLY PLACED in a three-quarter POSITION (45 degrees from the front of the object and 45 degrees up from the center LINE, which is OFTEN USED AS a SET POINT), it CAN also come from below or behind the object, or anywhere else, depending on the scene. The key light is usually the first light to be placed and used to create the initial lighting effect in the scene.

Although the initial placement provides a good way to illuminate the object, the result is really a dull and uninteresting image. The shadows are usually rough and sharp. Again, the scene always looks too dark because there is no natural ambient light to brighten the shaded areas. This is useful for certain scenes, such as night scenes, but for most scenes, it is not appropriate.