Hard Light

The term for a lighting source which produces light with a hard shadow pattern.

Examples of a hard light source are:

Direct sunlight, unfiltered by any cloud cover.

An open faced lighting unit such as a Redhead or Arri 800 watt

A fresnel lens lighting unit such as a Pup, 2k Fresnel, 2.5k HMI

Hard light is used when very directional lighting is required. For example to simulate sunlight.