Beam spread is the angle of the beam of a luminaire or reflector lamp. It is determined by the design of the reflector. Luminaires with a narrow beam spread illuminate small areas brightly. Light sources with a wide beam spread illuminate large areas but less brightly. Luminous intensity falls to half the maximum value in the opening angle.

For uniform illumination (general lighting, task lighting), wide-angled luminaires with large beam spreads are used. For accent lighting, a more focused beam of light is required. Wide-angled lamps and luminaires are referred to as "floods" or "wide floods", those emitting a highly focused beam with a narrow spread – e.g. 10° – are termed "spots".