Lumen
A lumen is a unit of measurement that is used to express how much illumination a light source provides. An easy way to illustrate this measurement is to imagine a birthday cake with candles. A lamp that puts out 1 lumen of light is as bright as 1 birthday candle. A lamp that puts out 100 lumens of light is as bright as 100 candles. Thus, the higher the amount of lumens the brighter the light.
Colour Rendering (CRI)
Colour rendering index (CRI) is a way of measuring how well a light source makes colours appear when viewed under the light source. In other words, it is a measurement of the light colour quality. The index ranges from 0 to 100. A light’s CRI can only be compared to another light if they have the same colour temperature. (See description below)
Colour Temperature
Colour temperature is the colour appearance of the light emitted by a source. The colour temperature of lights can generally be categorised as warm, neutral or sources. Normally, the lower the colour temperature the warmer the light appears and vice versa. Measuring colour temperature is expressed on the Kelvin scale (K) see diagram.
Design Lifetime
Design Lifetime is the average life of a lighting product when operated at nominal lamp voltage. A light’s life span will depend on what type of light it is. Incandescent lightbulbs are very cheap but will last approximately one year. In contrast LEDs have a high initial cost but will not need to be changed for thirty years.
Luminous Efficacy
Luminous efficacy measures how efficient a light source is at converting electricity power to light. It is measured in lumen output per unit power input (watt). Efficacy = lumen / wattage
Incandescents = 12.8 lm/W
Halogens = 14.4 lm/W
Compact Fluorescents = 45 lm/W
Brightgreen LEDs = 68 lm/W
Beam Angle
Beam angle refers to a light source’s measure of spread which is measured in degrees. A light’s beam angle is determined when its lux level drops to half of the intensity of the centre beam (see diagram). Beam angles are commonly 15, 30, 45 and 60 degrees.
Lux
Lux is a measurement of the light intensity falling on a surface. This measurement determines the brightness of a light in a space and is dictated by the Australian standards. Lux meters are available to determine lighting levels and evaluate the energy efficiency of lighting designs.
• 1 lumen per square meter equals 1 lux.
• 1 lumen per square foot equals 1 footcandle.
Daylight Harvesting
Daylight harvesting is a technology that senses and recognises light levels as they change throughout the day. A daylight harvesting sensor automatically dims LED lights to maintain an exact light level depending on the amount of light needed in that room at that time.
Dimmability
Whether or not lights are dimmable will affect the range of light levels they can produce. Dimmable lights allow light to be adjusted to the right intensity and deliver different amounts of light for different occasions and times, changing the ambience and mood of a space.
Gimbal
A light that is gimballed allows the direction of the light to be adjusted to a certain degree. Gimbals are useful if you need the light to be projected in a certain direction, i.e. if light needs to point down a hallway.
Watt
A watt is a unit of electrical power. We measure electrical usage in watts and pay for our electricity by the number of watts we use. Typically a standard halogen incandescent bulb operates at 50 watts. In contrast LEDs can be just as bright while using about a quarter of the watts.
