underillumination

Underillumination is the practice or phenomenon of illuminating a subject or surface from sources located beneath it. In architectural, stage, and photographic contexts, underillumination creates light that rises over the lower edges and highlights contours that would be less visible from above. The term is sometimes used interchangeably with underlighting or underlit lighting, though usage varies by field.

Common implementations include architectural and landscape lighting with floor-level fixtures, recessed floor lights, and ground-based luminaires aimed upward at walls or objects. In theater and cinema, floor-mounted fixtures such as footlights project upward to sculpt figures and set pieces. In photography, underlighting is achieved with small strobes or LEDs placed below the subject, often softened with diffusers to control contrast. Underwater photography and submersible lighting also employ lights positioned beneath the subject to create buoyant, upward illumination.

Underillumination tends to produce upward shadows and can emphasize undersides and textures, creating a dramatic or eerie mood. It can flatten facial features if overused and is generally less flattering for traditional portrait lighting. In architecture or exhibitions, underlighting can intensify color saturation on vertical surfaces and produce a halo or glow along bases, contributing to spatial perception and atmosphere.

Historically, underillumination has been used in stage lighting and in film noir to suggest mystery or threat. Advances in LED technology and compact, controllable fixtures have broadened its practical applications, including safety lighting, architectural accents, and decorative effects. Designers must consider glare, energy use, and light pollution when planning underillumination.

See also: up-lighting, downlighting, footlights.