Lighting Terminology Unravelled

Engineers can tend to use a lot of jargon and one thing I like to do is de-myth some of the stuff that might leave you baffled.  Hope you find this useful.

CRI = Colour Rendering Index – essentially this is a measurement of light colour quality – it ranges from 0 to 100 and the higher the number the better the quality – the better your ability to determine the true colours of the things you are looking at.  By way of example, sodium street lighting has a low CRI and that is why cars tend to look the same dull grey under yellow street lights — change them to high CRI LED and lo, you can tell the difference between a red car and a brown car.

Colour Temperature – in terms of commercial lighting there are really only three temperatures you need to know about – “warm white” (around 2700K), “cool white” sometimes called “natural” which is 4000K and “daylight” which is 5700K-6000K.  If you are interested the K are Kelvins.  Warm white is best kept in the home in my opinion, reserved for those rooms where colour rendering is not important, so the lounge for example and the bedroom.  Cool white is a great colour for a host of uses and I am now a convert to 4000K in the retail environment.  Daylight can be stark as there is a lot of blue in the output but this can be advantageous in the office environment where it provides a very visually comfortable environment although it can take some getting used to.

DALI – this is just a form of digital control and dimming.

Dimming – a form of control that varies the brightness of lighting and yes – you will save money by dimming but the lamps in the dimming circuit must be “dimmable” and not all lamps or LEDs are so be careful to check that the word DIMMABLE appears on the box.