Selecting the right lamp often can be a daunting task given the numerous factors a designer must take into account. There are external considerations such as price and recycling options. But when it comes to source performance, the designer must first consider the lamp base; next, the shape and treatment of the envelope, or bulb; and finally, the illumination source itself. Common sources include incandescent, fluorescent, metal halide, and high- and low-pressure sodium. Each source type is associated with a particular application. Traditionally, incandescent is used for residential scenarios because of its pleasing warm color temperature and high color rendering capabilities. Fluorescent sources often are found in hospital, office, and institutional settings because of their lower maintenance and operating costs. Exterior spaces commonly are lit with metal halide and high-pressure sodium. Low-pressure sodium use is diminishing, but is still found on certain roadways and in parking lot applications.

The outline that follows aims to create a quick reference guide that categorizes the primary illumination sources used in lighting design today. One source not listed is light-emitting diodes (LEDs). The popularity and efficiency of these miniature point sources is escalating at great speed, and advances in solid-state lighting technology and manufacturing is happening almost weekly. Housings and optics for LED-based luminaires is just now beginning to correspond to the specifics of this unique light source, and its light characteristics demand different evaluation criteria when it comes to source selection for design applications.

INCANDESCENT

Source: Standard filament, standard voltage
Shapes: A, G, P, S, and T; reflector lamp; ellipsoidal reflector lamp
Applications: Used in residential, hospitality, and retail illumination because of its warm color and low cost.
Wattage: 1–500
Distribution: Clear: point source, general | Frosted: diffuse, general | Spot or flood: directional

Source: Tungsten halogen
Shapes: Halogen A-lamp; small bi-pin; double ended; PAR
Applications: A more efficient and longer-life substitute for the standard filament. Halogen lamps have more light in a smaller envelope.
Wattage: 1–1,000
Distribution: Clear: point source, general | Frosted: diffuse, general | Spot or flood: directional

Source: Tungsten halogen, low-voltage
Shapes: Miniature bi-pin capsules, MR and PAR
Applications: Seen in residential, hospitality, retail display, museums and galleries, and landscape lighting where beam control is important and accent lighting is desired.
Wattage: 1–100
Distribution: Clear: small point source, general | Spot or flood: directional

FLUORESCENT

Source: Electric arc, ballast
Shapes: Linear, circular, and U-bent
Applications: The choice light source for institutional and commercial buildings because of their low cost and energy efficiency.

Source: Electric arc, ballast
Shapes: pcl, pl
Applications: Used in downlighting in commercial and institutional spaces.

Source: Electric arc, self-ballasted
Shapes: Compact Edison base
Applications: A good alternative to the standard incandescent lamp if energy efficiency is more important than light quality.

Source: Electric arc, ballast, cold cathode
Shapes: Not applicable
Applications: Can be formed into any shape and color of light. Typically used for covelighting and building outlining; also can be shaped and formed as required.

Source: Electric arc, transformer, neon
Shapes: Not applicable
Applications: Commonly used for color accents in signage and special effects.

Source: Radio waves, generator and power coupler, induction
Applications: Street lighting, pedestrian lighting, and areas that are difficult to maintain.


Distribution: 55–165
Wattage: 2,700–4,000
CRI: 80
Dimming: Non-dimmable
Average lamp life (h): 100,000
Lumen loss over time: Very good
Efficacy (lm/W): 50–60

HIGH-INTENSITY DISCHARGE (HID) Source: Mercury, ballast
Shapes: BT, E, ED, ET, PAR, and R
Applications: An older source, still seen in security lighting and some streetlights.
Distribution: Clear: point source, general | Spot or flood: directional
Wattage: 50–1,000
Color temp (K): 3,200–7,000
CRI: 20–45
Dimming: Possible with additional equipment and a special circuit.
Average lamp life (h): 16,000–24,000
Lumen loss over time: Fair
Efficacy (lm/W): 25–65

Source: Metal halide, ballast
Shapes: BD, BT, E, ED, ET, and T
Applications: Standard metal halide sources are used in lighting parking lots, streets, landscapes, building façades, and sports arenas.
Distribution: Clear: point source, general

Source: Metal halide, ballast
Shapes: Ceramic metal halide: PAR, MR, AR111, R
Applications: Ceramic metal halide sources are being used in retail, display, and commercial buildings because of the improved color temperature and CRI.
Distribution: Spot or flood: directional

Source: High-pressure sodium, ballast
Shapes: BD, BT, E, ED, ET, and T
Applications: roadway lighting, tunnels, parking lots, and industrial workspaces.
Distribution: Clear: point source, general
Wattage: 35–1,000
Color temp (K): 1,900–2,700
CRI: 21–65
Dimming: Possible with additional equipment and a special circuit.
Average lamp life (h):16,000–40,000
Lumen loss over time: Very good
Efficacy (lm/W): 40–140

Source: Low-pressure sodium, ballast
Shapes: Not applicable
Applications: An older source, still seen in security lighting and some roadway lighting.
Distribution: Clear: point source, general
Wattage: 18–180
Color temp (K): 1700
CRI: Not applicable
Dimming: Non-dimmable
Average lamp life (h): 18,000
Lumen loss over time: Very good
Efficacy (lm/W): 100–180