Luminaire or Lighting Fixture
A luminaire is “a complete lighting unit consisting of a lamp or lamps together with the parts designed to distribute the light, to position and protect the lamps, and to connect the lamps to the power supply”. This is the industry standard definition provided by the Illuminating Engineers Society (IES), however, it is generally interchangeable with the term lighting fixture.
Power factor is an expression of energy efficiency of the electrical system and measured as a % or value between 0.0 and 1.0 e.g. 0.97 = 97% energy efficient.
Lumen (lm). A lumen is a measure of the total quantity of visible light emitted by a source per unit of time. Basically, the higher the total lumens, the brighter the light. A traditional 60-watt incandescent bulb would create 800 lumens, conversely, our 85-watt LED fitting creates 10,500 lumens.
A lux is a unit of illumination the amount of light that falls on a surface, being one lumen per square metre. The closer you are to a light source the higher the lux reading will be. The lux level is important for task lighting to ensure that there is sufficient light falling on the work area. For example, an office may typically require 500 lux compared to a workshop for detail work at 750 lux.
System Efficacy or Lumens Per Watt (lm/W)
This metric takes the total light output in Lumens and divides it by the power usage in Watts giving the amount of light emitted by one Watt. The higher the lumen output per watt, the more efficient the fitting is at creating light from electricity, saving potential electricity expense.
Median Useful Life and L/B Values
The light output from all light sources decreases over time therefore it is helpful to have a measure of this, known as the median useful life, to compare various fittings. The median useful life is the total operating time at which under normal conditions at least 50% (this is indicated as B50) of a large group of initially installed products is expected to still be operating at a particular % of the initial lumens (this is the L component). Hence an LED light fitting with a rating of 55,000 hours B50/L70 means at 55,000 hours of operating at least 50% of the LEDs will still be operating at 70% of their initial lumens.
It is generally accepted that a light output of 70% of initial lumens is the threshold for human perception of changes in light levels and for this reason the generally accepted lifetime metric for LED light sources is L70. Therefore, if a light fitting only states a number of hours e.g. 50,000 hours it will typically be on a B50/L70 basis.
Colour Rendering Index (CRI)
The Colour Rendering Index (CRI) measures the ability of a light source to accurately reproduce the colours of the object it illuminates, basically the colour quality of the light. A score of 100 is the maximum possible with 80 CRI generally the baseline for acceptable colour rendering in most indoor and commercial lighting applications. A CRI of 90 or above may be required for professional or aesthetic reasons for printing and paint shops or photography studios and high end retail environments.
Correlated Colour Temperature (CCT)
Correlated colour temperature (CCT) is the relative warmth or coolness of light and is measured in degrees Kelvin (K). A lower number in the 2,000-3,000K range is often called “warm white” with orange to yellow-white appearance. A range of 3,500-4,500K may be described as “cool” or “bright white” and be neutral to possibly slightly blue in tint. A CCT of 4,500K and above is the “daylight” temperature range which is best for task lighting.
IP rating refers to ingress protection rating or international protection ratings, which are used to classify levels of dust and water sealing effectiveness. An IP65 rating means the fitting is fully dust tight and has complete protection against solid objects and protection assured against water jets projected by a 6.3mm nozzle from any angle.
The spread of light, measured in degrees. The light beam angle is determined when its lux level drops to half of the intensity of the centre beam.
AS/NZS 60598.1 is the Australian and New Zealand standard specifying general requirements and tests for luminaires incorporating electric light sources for operation from supply voltages up to 1,000V.
An IES (Illuminating Engineering Society) file is a photometric data file that is composed of lighting intensity and luminosity and used for simulating lighting systems before they are installed.