Lighting terminology

Ambient Light – Blanket light level or general Illumination that comes from all directions in a room that has no visible source.

Brightness – is what the eye detects and the brain interprets as light thus affecting the size of your iris.

Colour appearance – The apparent colour emitted by a light source, measured by correlated colour and described as warm, intermediate, cool or cold.

Colour Temperature – Measured in Kelvin, this is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics and other fields. In the lighting industry we use 2700K Warm white, 3000K White, 4000K Cool White or 6000K Daylight.

Colour rendering – The ability of the light from the light source to reveal the colours of an object. It is determined by the spectrum of the light source. Measured by colour rendering index (Ra) and the higher the number the better, up to a maximum of Ra = 100. LED’s normally have a Ra 80 / 85 but can now be supplied with a Ra 95 at a cost.

Contrast – subjective experience of comparative brightness between areas of luminance seen simultaneously. The difference between light and dark.

Glare – UGR The discomfort or impairment of vision experienced when there is excessive contrast in the field of vision.

Scallop – An effect created by the light distribution when close to a surface, this is often used in design.

Wall wash – Even distribution of light dedicated to illuminate a wall, you will see this in alot or my designs.

Spot – Narrow beam of light to illuminate an object.

Flood – Large beam of light and illumination with more even distribution of light.

Illuminance – The amount of light falling on an area divided by the size of that area. (also known as the “density of the light”) measured in lux, varies from 0.2 lux by moonlight to 500 lux for office lighting to 100,000 lux by bright summer sunlight.

Luminance – The measured brightness of a luminous or illuminated surface. Measured in cd/m².

Lux – is the SI unit of illuminance and luminous emittance, measuring luminous flux per unit area. It is equal to one lumen per square metre.

Lumen – a measure of the total “amount” of visible light emitted by a source AKA luminous flux.

Luminous efficacy – The ratio between the luminous flux or Lux emitted by a light source to the power consumed by the source. This is important to the industry and measured in terms of lumens per watt (lm/W) for Part L compliance.

LOR – Light output ratio is a measurement published by lighting manufactures to show the final amount of emitted light from the luminaire.  This is key and the responsibility of a competent designer to check for Part L compliance and other standard governing bodies.

Luminous flux – The rate light is emitted by a light source measured in lm known as Lumens.

Luminous intensity – The amount of luminous flux radiated in a particular direction, measured in cd or lm depending on the light spectrum.

Task Lighting – to increase illuminance of a local and defined area for reading, theatre or desk works.

Uniformity – The ratio of the minimum illuminance to the average illuminance over a specified area.

Switching – Reference to the type of control to lighting powered by a circuit.

Dimming – adjustable light output from 0% to 100%.

Circuit – Lighting connected via one cable that can be individual from others.

Channel – The circuit that is connected to a breaker or control system.

Chromaticity – of an LED product – that is, degree of deviation of its colour temperature – is defined in MacAdam ellipses in Standard Deviation of Colour Matching (SDCM) as per the CIE 1964 standard. The MacAdam system originates from the United States and ranks colour quality on a scale of 0 to 10.

CTT – correlated color temperature, this refers how we preserve warm white 3000K and below to cool white 4000K and above measurements in Kelvin.

MacAdam  1 to 3 step – Macadam 2 SDCM: museum, gallery application Macadam 3 SDCM: office, school, retail, healthcare applications. Divation from a chromatic diagram steps 1 to 3 is not noticable by the untrained eye.

MacAdam  – Macadam 3 SDCM: outdoor facade / Macadam 5 SDCM: other outdoor applications. 5 step is noticeable but for outdoor applications it fine unless you want to illuminate a white wall. Mcadam step 4 is quite often a fluorecent lamp.

ECA – Enhanced Capital Allowance ( ECA ) scheme.

Please contact Stuart Moth to arrange a presentation to educate your staff on the lighting basics.

 

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