Bulb shapes, sizes, and terms
Incandescent light bulbs come in a range of shapes and sizes. The names of the shapes may be slightly different in some regions. Many of these shapes have a designation consisting of one or more letters followed by one or more numbers, e.g. A55 or PAR38. The letters represent the shape of the bulb. The numbers represent the maximum diameter, either in eighths of an inch, or in millimetres, depending on the shape and the region. For example, 63 mm reflectors are designated R63, but in the U.S. they are known as R20 (2.5 inches). However, in both regions, a PAR38 reflector is known as PAR38.
Common shapes:
- General Service
- Light emitted in (nearly) all directions. Available either clear or frosted.
- Types: General (A), Mushroom
- High Wattage General Service
- Lamps greater than 200 watts.
- Types: Pear-shaped (PS)
- Decorative
- lamps used in chandeliers, etc.
- Types: Candle (B), Twisted Candle, Bent-tip Candle (CA & BA), Flame (F), Fancy Round (P), Globe (G)
- Reflector (R)
- Reflective coating inside the bulb directs light forward. Flood types (FL) spread light. Spot types (SP) concentrate the light. Reflector (R) bulbs put approximately double the amount of light (foot-candles) on the front central area as General Service (A) of same wattage.
- Types: Standard Reflector (R), Elliptical Reflector (ER), Crown Silvered
- Parabolic Aluminized Reflector (PAR)
- Parabolic Aluminized Reflector (PAR) bulbs control light more precisely. They produce about four times the concentrated light intensity of General Service (A), and are used in recessed and track lighting. Weatherproof casings are available for outdoor spot and flood fixtures.
- 120V Sizes:PAR 16, 20, 30, 38, 56 and 64
- 230V Sizes:Par 38, 56 and 64
- Available in numerous spot and flood beam spreads. Like all light bulbs, the number represents the diameter of the bulb in 1/8s of an inch. Therefore, a PAR 16 is 2″ in diameter, a PAR 20 is 2.5″ in diameter, PAR 30 is 3.75″ and a PAR 38 is 4.75″ in diameter.
- Multifaceted Reflector (MR)
- HIR
- “HIR” is a GE designation for a lamp with an infrared reflective coating. Since less heat escapes, the filament burns hotter and more efficiently.The Osram designation for a similar coating is “IRC”.