Light Sources

The performance of any light fixture depends very much on the light source (bulb) used. Different sources produce different effects. Light is measured in terms of:

Wattage
The amount of electricity consumed by a bulb.

Lumens
The amount of light that a bulb produces.

Footcandles
The amount of light reaching a subject.

Incandescent

General Service

General service bulbs are inexpensive and readily available in a variety of wattages and shapes. They produce a yellowish-white light that is emitted in all directions. Available in either clear or frosted.

Types:

• General (A)
• Globe (G)
• Decorative (D)
• (flame, teardrop, and other shapes)

Reflectorized

Reflective coating inside the bulb directs light forward, giving you better beam control than general service bulbs. Flood types (FL) spread light. Spot types (SP) concentrate the light.

Reflector (R) bulbs put approximately double the amount of light (footcandles) on the subject as General Service (A) of same wattage.

Parabolic Reflector (PAR) bulbs control light more precisely. They produce about four times the light of General Service (A) and are used in recessed and track lighting. Weatherproof casing makes them suitable for outdoor spot and flood fixtures.

Tungsten-Halogen

Produces a bright, white light. Has longer life and provides more light (lumens) per watt than regular incandescent bulbs. Maintains maximum efficiency throughout life of bulb. Available in both line- (120 volts) and low-voltage (12 volts). Low-voltage types require a transformer to step down the voltage. Among the most popular tungsten-halogen bulbs are:

Line Voltage

PAR 16, 20, 30 and 38 reflectorized bulbs provide better beam control than regular incandescent PAR bulbs. Available in numerous spot and flood beam spreads. Used in track, recessed, and outdoor spot, and floodlights.

T-3 Double-Ended bulbs are available in a variety of base types and are used in wall sconces, torchiers, and outdoor flood lights. The direction of the light is controlled by the fixture.

T-4 Single-Ended bulbs come in both “mini-can” and “bayonet” base types and are used in wall sconces, bath brackets, torchiers, and pendants. The direction

Low-Voltage

MR-11, MR-16 (Mini-Reflectors) provide excellent beam control. Available in numerous spot and flood beam spread. Miniature size permits use in smaller track and recessed fixtures. Also used in outdoor spotlights.

PAR-36 provides superior beam control, especially over longer distances. Available in a broad selection of spot and flood beam spread. Used in track, recessed, and outdoor fixtures.

T-4 Bipin, also known as a “peanut” bulb, is a miniature lamp used in pendants, halogen desk lamps, and some track fixtures. The direction of the light is controlled by the fixture.

Fluorescent

Use 1/5 to 1/3 as much electricity as incandescents with comparable lumen ratings and last up to 20 times longer. Compact types are used in smaller, trimmer fixtures such as recessed downlights, wall sconces, close-to-ceiling fixtures, and track lights. Screw-in types can be used in place of incandescents in standard lamp sockets. Available in a wide spectrum of colors. Warm white tones best duplicate the color of incandescents.

Copyright © 2003 American Lighting Association