Light Source Types

The performance of anylight fixture depends very much on the light source (bulb) used. Different bulbs produce different lighting effects, and many bulbs have widely varying performance. To save energy, select the most efficient light bulb that will provide the type of lighting you need.

Lighting Measurements Terminology

Wattage: The amount of electricity consumed by a light source

Lumens: The amount of light that a light source produces

Efficacy: Lumens per watt

Footcandles: The amount of light reaching a subject

Types of Bulbs

Incandescent Bulbs

Incandescent bulbs produce light when an electric current passes through a filament and causes it to glow. Because they are less energy efficient than other light sources, they are best used for task lighting that demands high levels of brightness.

Fluorescent Bulbs

Fluorescent bulbs produce light when an electric arc passes between cathodes to excite mercury and other gases producing radiant energy, which is then converted to visible light by a phosphor coating.They 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.

Today's fluorescent bulbs come in a wide selection of sizes and can produce warm tones of light similar to those of incandescents.

High-Intensity Discharge (HID) Bulbs

High-Intensity Discharge (HID) bulbs produce light when an arc passes between cathodes in a pressurized tube, causing metallic additives to vaporize. They have long lives and are extremely energy efficient, but - with the exception of metal halides - they do not produce pleasing light colors. In residential settings, HIDs are most often used for outdoor security and area lighting.

There are four types of HIDs:

Metal Halide

High-Pressure Sodium

Low-Pressure Sodium

Mercury Vapor

LEDs

Light Emitting Diodes (LEDs) produce light when voltage is applied to negatively charged semiconductors, causing electrons to combine and create a unit of light (photon). In simpler terms, an LED is a chemical chip embedded in a plastic capsule. Because they are small, several LEDs are sometimes combined to produce a single light bulb.

LED lighting in general is more efficient and longer lasting than any other type of light source, and it is being developed for more and more applications within the home. LEDs are currently popular in under-cabinet strips and some types of down-lights.