Lighting Fixtures Fundamentals
Definition
Each family of lighting fixtures shapes light in a specific way. A PAR (parabolic aluminised reflector) produces a wide, soft-edged beam with little control over its shape; it is inexpensive, bright and suited to broad colour washes and strong looks where precision is not required. An ellipsoidal reflector spotlight, called a profile in Europe and often a Leko in North America, produces a hard-edged, focusable beam that can be shaped with shutters and can project gobos, which makes it the usual choice for tight specials, framing scenery and projected textures. A Fresnel, named after its stepped lens, gives a soft-edged beam that can be adjusted from flood to spot, and is a classic key light in theatre, film and television.
The guide
Two angles describe a beam. Following the IES definitions, the beam angle is the angle within which intensity stays at or above 50 percent of the maximum, and the wider field angle is the angle at which it falls to 10 percent. A narrow beam concentrates light for long throws, while a wide beam spreads it for coverage. The Beam / Photometric tool calculates the relation between angle and throw distance.
A fixture chosen for the wrong task produces spill where containment was needed, a soft edge where a sharp cut was needed, or too little control for the shot. The choice follows the requirement, whether broad coverage, a hard edge or a projected texture.
The rule
The fixture type is chosen from the coverage, edge and texture that the task requires.
Glossary terms
Sources
- Beam angle (Wikipédia, pointeur secondaire), définition IES : angle à 50 % de l'intensité maximale, angle de champ à 10 % · en.wikipedia.org
- AGi32 Photometric Toolbox, rapport IES : angles de faisceau et de champ · docs.agi32.com
- Ellipsoidal reflector spotlight (Wikipédia, pointeur secondaire) : découpe, couteaux, gobos, appellation Leko · en.wikipedia.org
- Fresnel lantern (Wikipédia, pointeur secondaire) : lentille à échelons, réglage flood/spot · en.wikipedia.org
- Parabolic aluminized reflector (Wikipédia, pointeur secondaire) : PAR · en.wikipedia.org