Contrast is the third most important characteristic of a photographic light. We say a light source has high contrast it its rays strike the subject from nearly the same angle. In a low contrast situation, the rays hit the subject from many different angles. A typical situation of a high contrast light happens with sunlight on a sunny, clear day. Typical of a low contrast lighting is a foggy, grey day. In high contrast lighting there are sharp and clearly defined shadows. In very low contrast situations, there are no shadows.

For single light sources, the size (or closeness) of a source is the primary factor that influences contrast. A small light source usually allows for high contrast lighting. A large light source (or one that is far away) gives off a more diffuse light, with lower contrast. These principles are particularly important when lighting for underwater photographs.