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Anyone who has seen a rock and roll show, an award ceremony or a theatre production has experienced the illuminating effects of spotlights. These are light sources that send out a cone of light. It has a defined conic volume and is used to illuminate objects within this conical volume. Torches, desk lamps and theater lights are all examples of spotlights, but most people think of the lights that are used in stage performances.
Seven types of spotlights categorized on the basis of their functionality include, the plano convex, ellipsoidal, Fresnel, Parabolic Aluminized Reflector (PAR), PAR Pin, Beam Projector and Followspot lights.
The plano convex light was first developed in 1870 and is the earliest form of a theatre lighting system using a single lens. It uses a plano convex lens which is convex, or round, on one side and flat on the other. This lens is contained in a simple housing that also contains a bulb and a reflector.
The ellipsoidal spotlight is the most widely used type of this lighting. Also known as a "Leko," it has the flexibility to light a broad area or concentrated spots. Normally, it produces a beam of light that is round in shape but that can be manipulated by the light's shutter, iris, or gobo. Shutters can change the shape of the beam of light and irises can be inserted to make the beam smaller. A gobo is a metal plate with cuts made in it to alter the shape of the light produced. Ellipsoidal spotlights usually have one lens but may have an additional lens. The lens position can be moved forward or backward to change focus, which results in a beam edge ranging from sharp and hard to soft.
The Fresnel spotlight is named after the French physicist Augustine Fresnel who designed the "Fresnel" lens. Fresnel lenses are mostly used in lighthouses. The single lens of the light provides lighting for a concentrated spot or broad area. These lights do not have the ability to project patterns like the ellipsoidal kind, and are more useful in providing flood lighting.
PAR (Parabolic Aluminized Reflector) spotlights are highly efficient, and have the reflector, filament and lens optically aligned and fixed positions. They are often used in music shows. The haze produced by haze machines and smoke created on the stage at a rock show, for example, makes the path of the PAR spotlight prominent. These are also used as top lights in theaters.
PAR Pin light is a low voltage PAR spotlight that lights up a very concentrated area. It is often used to highlight particular spots like an actor’s face, a gun or a picture on the stage after dimming the general lighting.
Beam projector spotlights don't have lenses and produce intense beams of light. They can be used to follow an actor on stage or to simulate sunlight and moonlight in shows.
Followspot lights are operated by a person, and are used to follow a performer on a stage. These are used more commonly in musicals, theaters and operas to highlight a single performer or group of performers by following their movements.