Definitions

Amperes ('Amps.')
A measure of electrical current. In incandescent lamps, the current is related to voltage and power as follows: Watts (power) = Volts x Amps (cutrent).

Average Lamp Life (Rated Lamp Life)
This is the manufacturer provided rating for the average expected life of a lamp. For most lamp types, rated lamp life is the length of time of a statistically large sample between first use and the point when 50% of the lamps have died. lt is possible to define 'useful life' of a lamp based on practical considerations involving lumen depreciation and color shift.

Base Type
The base is the end of the lamp that fits into the receptacle connected to the electrical supply. There are many types of bases used in lamps, screw bases being the most common for incandescent and HID lamps, while bi-pin bases are common for linear fluorescent lamps.

Beam Spread
The angular dimensions of the cone of light from reflectorized lamps encompassing the central part of the beam out to the angle where the intensity is 50% of maximum. The beam angle sometimes called "beam spread" is often part of the ordering code for the reflectorized lamps.

Bulb Type
The bulb type refers to the shape and class of the bulb.

Color Rendering Index (CRl)
An international system used to rate a lamp's ability to render object colours. The higher the CRI (based upon a 0-100 scale) the richer colours generally appear. CRI ratings of various lamps may be compared, but a numerical comparison is only valid if the lamps are close in colour temperature. CRI differences among lamps are not usually significant (visible to the eye) unless the difference is more than 3-5 points.

Colour Temperature
Number indicating the degree of 'yellowness' or 'blueness' of a whitelight source. Measured in kelvins, Colour Temperature represents the temperature an incandescent object (like a filament) must reach to mimic the colour of the lamp. Yellowish-white ('warm') sources, like incandescent lamps, have lower colour temperatures in the 2700K-3000K range; white and bluish-white ('cool') sources, such as cool white (4100K) and natural daylight (6000K), have higher colour temperatures. The higher the colour temperature the whiter, or bluer, the light will be.

Cool White
A term loosely used to denote a colour temperature of around 4100K. The Cool White (CW) designation is used specifically for T12 and other fluorescent lamps using halo-phosphors and having a CRI of 62.

Daylight Lamp
A lamp resembling the colour of daylight, typically with a colour temperature of 5500K to 6500K.

Dimmable
Whether or not the lamp lumens can be varied while maintaining reliability.

Flood
Used to refer to the beam pattern of a reflector lamp, which disperses the light over a wide beam angle, typically 20 degrees or more. ('Flood' as opposed to 'spot').

Halogen Lamp
A halogen lamp is an incandescent lamp with a fllament that is surrounded by halogen gases, such as iodine or bromine. Halogen gases allow the filaments to be operated at higher temperatures and higher efficacies. The halogen participates in a tungsten transport cycle, returning tungsten to the filament and prolonging lamp life.

Kelvin
A unit of temperature starting from absolute zero, parallel to the Celsius (or Centigrade) scale. 0C is 273K.

Lumens
A measure of the luminous flux or quantity of light emitted by a source. For example, a dinner candle provides about 12 lumens. A 60-watt Soft White incandescent lamp orovides about 840 lumens.

MR-16 and MR-11
A line of low voltage compact reflector lamps used for accent and spot lighting. The 16 and 11 refer to 16 eighths of an inch diameter and 11 eighths.

Orientation (also Operating Position or Burn Position)
Mercury and High Pressure Sodium lamps may be operated in any burn position and will still maintain their rated performance specifications. Metal Halide and Low Pressure Sodium lamps, however, are optimized for performance in specific burn positions, or may be restricted to certain burn positions for safety reasons.

Soot
A colloquial term referring to a reflector lamp with a tight beam of light, typically around 10 degrees or less. lt comes from the fact that such a lamp produces a narrow spot of light as opposed to a wide flood of light.

Volt
A measure of 'electrical pressure' between two points. The higher the voltage, the more current will be pushed through a resistor connected across the points. The volt specifcation of an incandescent lamp is the electrical 'pressure' required to drive it at its designed point. The 'voltage' of a ballast (e.g. 277V) refers to the line voltage it must be connected to.

Warm White
Refers to a colour temperature around 3000K, providing a yellowish-white light.

Watt
A unit of electrical power, Lamps are rated in watts to indicate the rate at which they consume energy.